# consolidation of Loss Gold thread



## 4metals (May 16, 2022)

I set up a refining system, but I have little experience. To know if I was on the right track, I wanted to report one of Refine operations.
Please help me about losing gold in this operation.


We performed refining operation using the AR method. Our input was 2610 grams; Analysis includes: 765 gold, 68 silver, 148 copper, 8 zinc, 4 nickel, 6 cadmium and some others.

We calculated the acid values to digest 7.5 ounces per liter of solution. Hydrochloric acid 32%, 9.3 liters and 2.3 liters of nitric acid 64%. We flaked the gold as much as possible. Then we poured it in Tumblr.

We added 7 liters of hydrochloric acid along with 1.3 liter of nitric acid.

We also added some hydrogen peroxide during the slow reaction. After one hour, the reaction was somewhat balanced, we added 3.5 liters of hydrochloric acid again and slowly we added 1.1 liters of nitric acid.

After four hours, the reaction was very low. I added about one kilogram of 46% white urea to neutralize nitric. About Urea , I have little experience with urea. I added until the bubbles on the surface of the solution diminished. I added a little water. Then I did not see a quick reaction by adding urea.



After a while, I added 12 liters of 4 C cold water. We waited for a while, then filtered the solution, left the silver chloride, and transferred the solution with water until the transfer path became clear. At the end of the Tumbler wash we had 111.38 gr unresolved gold.

In the case of solid gold residue, I did not notice washing it with ammonia. Because they were not covered with anything. I first tested them with XRF and then melted them, their assay was 771 Au.


I Approximately 1.8 liters of 55% hydrazine is dissolved in 2.2 liters of water and Slowly add to solution in half an hour.

Add the flocculate , leave the solution for 12 hours.



The liquid became green and clear, we filtered the liquid into a secondary tank(with Fabric polypropylene), took all the pure gold. Then we washed the gold powder with hot water. Then we dried the gold powder in a steel container.

We filtered the solution with two polypropylene cloth filters. We did not use a paper filter, of course I like the paper filter because it does not absorb. We took more than 98% of the solid particles from the first fabric filter and the rest from the second filter. We thoroughly washed the filters. Some gold precipitated, we took it and sent the remaining liquid to the second tank.



Stannous test, when the gold was sitting on the bottom of the solution, I tested the solution on top of that gold. The answer was negative.

Unfortunately, after filtering the solution, I did not try again.

Also, all the water has been added to them while washing, now it may be close to 200 liters.

I added some aluminum to the solution and mixed it and let people do it.



I need to learn more about Stannous testing, it's very important. I have never had a positive Stannous test.



After melting and XRF test, the purity of gold was 999.6 Au and it was shown in the analysis 0.4 cu cu and no silver Ag. (But it seems not enough washing) because the surface of gold bullion was not best quality, Their surface is star-shaped impurities.



We dried the gold powder in a steel container, then melted it in an induction furnace with a new plant.



After accounting, we do not have *12.6 grams *of gold. I'm surprised, all the steps went well, no errors, and I'm sure of the scrap analysis. There may be some during the initial dubbing and gold powder, but we were careful and definitely not a lot. We have two places still left, silver chloride, the second bunker deposit.



I added two sheets of *aluminum* to the second bunker.



Then we mixed well every few hours. We added flocculate and left for another day.



we filtered the place, the amount of jelly powder had accumulated on the bottom of the bunker.



We took it and heated it in a steel pan and it was almost dry.



We tested with XRF. Showed *30/1000* gold.


We transferred the rest of the solution to the third bunker and added the aluminum again.

So far, 12.6 grams of that lost gold, 3.6 grams in the second bunker have been deposited in the sludge, so our lost gold is about 9 grams.



How to get the gold in this purple powder?



My friend told me ,that powder put in reactor for next part refining. Is it ok?



So far there is some gold in silver chloride and maybe in the third bunker solution.



Dried silver chloride is about *170 grams,* but I know the silver get is much less, right?

XRF testing of silver chloride showed that *98*_*/1000*_ of it contained gold.



In the third bunker, after filtering, sludge containing 2/1000 gold was taken.(Almost very little)



Here I want the best way to recover the silver chloride to get the gold trapped in it and recover the silver.



*Where do you think gold has gone?



This is important for any refiner.



It will not be economical to continue with these calculations.



Can you help find the deficit and control the various steps for possible corrections?*


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## 4metals (May 16, 2022)

These are the photo's of the system shared by the OP.


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## 4metals (May 16, 2022)

We can best serve the needs of the OP by starting at the top of his descriptions and both clarifying his process and making suggestions for discussion. Any additional photo's can further benefit this thread. 

I'll invite others to start and do my best to keep this on the rails and work towards a successful resolution of the OP's problems.

I realize there are questions we may have which can only be answered by the OP, by example what was the flocculant used and quantity. His participation is necessary for a successful resolution.


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## nickvc (May 16, 2022)

It’s possible with the cloth filter that with fine particles the loss may well be there , he could pour a weak AR solution through the filter and see what is actually there.


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## 4metals (May 16, 2022)

There are questions I have based on the terminology he has used. for example what is a gold sedimentation bunker and at what phase of the operation is it used. I am familiar with the italian systems called tumbler plants which are quite similar and they look like this;


In much the same way the solution drains from the drum and is filtered through a filter media. I would expect the manufacturer to have supplied or sourced proper filter media for both the aqua regia filtration before precipitation and after. 
There are also in line filter canisters used which are notoriously difficult to rinse free of values. where in the line are these filters? More details will be both informative for our members and helpful for the OP.


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## 4metals (May 16, 2022)

> "We calculated the acid values to digest 7.5 ounces per liter of solution. Hydrochloric acid 32%, 9.3 liters and 2.3 liters of nitric acid 64%. We flaked the gold as much as possible. Then we poured it in Tumblr.
> 
> We added 7 liters of hydrochloric acid along with 1.3 liter of nitric acid.
> 
> ...



Let's start step by step to review what was done here. First off as a rule of thumb for every liter of aqua regia you will dissolve 7.5 ounces of metal. 

starting with 2,610 grams. 2610/31.103 = 83.9 ounces. let's call it 84

84/7.5 = 11.2 liters of aqua regia.

since you have a chilled condensed vessel some of the nitric will recondense back into the reactor so you can get by with a 4:1 aqua regia mix. 4 parts Hydrochloric Acid one part Nitric Acid 

Thats 5 parts total. so...... 11.2 liters total divided by 5 is 2.24

This means you add 4 times 2.24 liters of Hydrochloric Acid which we round up to 9 liters. This should be all the aqua regia you require. Your total Nitric Acid addition should be 2.24 liters which should be roughly divided into 3 equal portions. 

All of the hydrochloric can be added from the start, along with 1/3 of the calculated nitric. The reaction will begin and once the reaction has risen and begins to subside, the second third of nitric should be slowly added. 
In a production environment (with the equipment you have) generally the full complement of acid is added to assure complete digestion. When the reaction again subsides, the last third can be added. Allow the reaction to go to completion at which time it should not be blowing any red fumes. 

Is this a heated vessel? Some manufacturers have heaters for tumbler plants. If you do it will assist with the rate of the reaction. 

I do not think it wise to add urea while it is in the tumbler plant. A better choice would be sulfamic acid. There are. many posts on the forum concerning its use and it will cause less issues down the line should your scrap contain any platinum group metals you wish to recover later. 

Once the reaction is complete I would cool it by throwing in ice. Ice has the benefit of chilling the solution and diluting it at the same time. Silver is much less soluble in cold solutions and is more likely to be eliminated as it will be captured by filtration when you filter the solution out of your reactor and transfer it to where you will precipitate the gold. 

What filtration is employed between the filter it drops into to be transferred to the precipitation tank. I believe it to be what you call the Silver Chloride filter and also the cylindrical filter. Please verify if this is correct.

On the silver chloride filter will remain all of your undissolved gold and all of your silver chlorides. The best method here is to rinse the chlorides and insolubles into a pail of water and store them in water until you are ready to process them. 

Please let's comment and question on the process up to this point before moving forward.


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## Martijn (May 16, 2022)

I got that same message in a private message and advised him to post it public. He only took part of it to the public forum as far as i know. 
I have way to many questions from that first long post. 
Hat's off for diving in


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## Gold.refinery (May 18, 2022)

Hi guys ;

I was finally able to convince my partners to share refining operation information. 
I am here to gain experience from gold refining specialists, I am ready to answer your questions step by step. Then I will ask my questions. 
We did another operation in the last few days. Some ambiguities remain for us, but I like not to raise issues sporadically.
I would like to ask *Dear* *4metal* to take these issues step by step. 
We have little experience, but we will succeed with you.


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## Elemental (May 18, 2022)

@Gold.refinery,

We are all here to learn and share knowledge. While I understand you came here looking for the help of our specialists, a major part of this forum is the free exchange of information and knowledge of refining from the hobby to industrial level. While I can appreciate your desire to keep you refining operations information as a cooperate secret, please understand that to ask questions here requires transparency so others may learn. 

If you seek the freely given information here, then please share freely as well. I have no doubt that many of our specialists would have no issues with contracting themselves out as consulting specialists, thus allowing for NDA's and the what-not at an expense to your business. 

That's my two-cents on that, I'll get off my soapbox and see if I can't put some math to your process and help out on the chemistry side as well.

Elemental


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## 4metals (May 18, 2022)

4metals said:


> Is this a heated vessel? Some manufacturers have heaters for tumbler plants. If you do it will assist with the rate of the reaction.





4metals said:


> What filtration is employed between the filter it drops into to be transferred to the precipitation tank. I believe it to be what you call the Silver Chloride filter and also the cylindrical filter. Please verify if this is correct.


Start with answering these 2 questions


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## Gold.refinery (May 18, 2022)

*1)*
In the last operation, all the feed was dissolved in 4 hours, except for 22 gr of 2900 gr.
No, Tumblr does not have a heating system. Just to help better reactivity at the beginning and end of the AR reaction, we add some hydrogen peroxide with Dosing pomp. 

*2)*
The solution to exit the Tumbler first reaches a polypropylene cloth filter (sucked by a diaphragm pump), then passes through it through a short path with a hose to a vertical cylindrical filter (as shown). And then pours into the tank for sedimentation operations.


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## 4metals (May 18, 2022)

The tumbler plants I am most familiar with are made by Italimpianti. The newer ones do have a heat option but it is a luxury and not necessary for karat gold refining. I have never found it necessary to add peroxide to get a good vigorous reaction in a tumbler plant. 

When you filtered the solution out of the reactor, sitting on the filter paper was what? Silver chloride and 22 grams of undissolved karat? Above you also said 111 grams. To avoid confusion here let's discuss one lot with all of the specifics. I am sure there is language translation going on here and I want to minimize confusion. The gold recovered as undissolved shot in your filter is not gold you lost as you accounted for it, it just needs to be refined. 

What we are looking for here from one of your original questions is gold that does not emerge from the system at the end. Gold that is lost to the process. For this lot that you have mentioned last, how much gold that was expected based on assay did not come out of the system?

When gold containing silver dissolves in aqua regia, it is not uncommon to have a small percentage of the gold mixed in with the silver chlorides. With a tumbler plant that number should be less than with a static motionless reaction. Generally silver below 7.5% will be low enough for an effective dissolve. Tumbler plant manufacturers say you can push that number up to 10% because of the mechanical contact breaking away silver chloride crusts. I have found this to be true in practice. If the size of the shot you dissolve is too large you will leave more values undissolved. 

When the solution is drained into your filter from the reactor, the solution contains most of the gold. I mentioned in an earlier post that a single drop of gold at today's prices is worth around 41¢ so it becomes critical to get as much of that liquid to the tank you will be precipitating the gold in. Based on your original alloy composition you were looking at green aqua regia. When you filtered everything through the filter, how did you assure yourself you got all of the liquid rinsed from the reactor? And once you pulled all of the liquid through the filter paper, what color was the paper? If it's green it is holding gold that will show up in the loss column. Until you are comfortable with the process you should learn the simple stannous chloride test well documented on this forum. The pumps and base of the filters also can trap liquids which hold gold. You need to open up the filter and check out the bottom to assure you are not leaving values behind. 


This is the inside of a typical filter, you can see it is easy to leave values behind without complete rinsing. And the smaller the lot, the larger the losses are. 

The filter path you showed also has a cylindrical filter in the line. These are difficult to rinse free of values. Here you should also test the filter with stannous chloride to make sure it isn't trapping solution. If you can, provide a photo of the system so we can see the path the loaded acid follows to your precipitation tank. it is critical that you can be sure you are rinsing that pathway clear of values. 

Before you drop your gold from solution, the volume of solution you lose can be as small as half of a small diners coffee cup and it will be all of the gold you are looking for. This is an area worth looking at. 

Please respond to these, and other questions you may be asked, before we move on the the chemistry of gold recovery.



Gold.refinery said:


> I would like to ask *Dear* *4metal* to take these issues step by step.
> We have little experience, but we will succeed with you.


One more thing, those who know me certainly know I am no dear! And I fully expect to hear from other members with hands on experience so we get a wider perspective on your system. 

And more photo's will help us to help you with your precipitation process as well as your cementation process you mentioned when looking for lost values.


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## snoman701 (May 18, 2022)

Rinse your AgCl with very dilute HCl until you get a negative stannous test. I cannot imagine running the above system without stannous. 4metals post should put it in perspective for a lot of people...a little bit of liquid is significant amount of money. Go get yourself a roll of 95% tin solder at the local hardware and make some.


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## Gold.refinery (May 19, 2022)

I never calculated the unresolved gold in the reactor as lost gold. 
I did 3 experimental refining operations in the last few days to gain experience. In the second operation, 111 grams of gold was not dissolved, in the third operation, 22 grams remained unresolved.

In the second operation, 12.8 grams of gold was not obtained. As mentioned, by dissolving some aluminum in the mother solution, I obtained 120 grams of sludge, which contained 30/1000 gold (approximately 3.5 grams gold), this sludge. I added to the feed in the third operation.

To ensure complete washing of the reactor, we have the possibility to open the door completely from the top of the reactor. And the reactor is thoroughly washed. We also take out the unresolved gold.
When all the solution came out of the primary silver chloride filter, it was gray, there was yellow liquid in some places, it was washed with water flow and suction pump, to make the hose route colorless.
The bottom of the filters, the way of the hoses, the valves, are washed together after each operation.

I will send the solution way from the reactor to the gold sedimentation tank.

*I will also answer your other questions about the calculation of chemical quantities (especially the amount of sediment),
we do a lot of this experimentally and See reactions with eyes , not computationally, this is not desirable. Because it pollutes the gold and adds the next steps.*


We have a Stannous test , but we do not know when to use it exactly . 
We have not seen a positive test so far. 
After filtering the solution, we wash silver chloride with hot water. We have never done washing with hcl. Maybe it's better to test the solution left in the hose with stannous, 
you mean?

*I have many questions*, but I'll answer your questions right now.


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## nickvc (May 19, 2022)

I think we should start right at the beginning of the whole process so
1 I’m assuming you are taking your numbers from an xrf reading hopefully from several areas at least top and bottom of the bar ? Is that correct ?
2 once you have your reading you then melt the bar into flake ? 
Do you dry and weigh that flake ? 
Im asking these questions because melting areas can be a major contributor to loses or put it another way if the gold doesn’t reach your reactor you can’t recover it.


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## Gold.refinery (May 19, 2022)

Hi nickvc
Yes of course , I test scrap gold bars from different areas, top and bottom, 
Some of them I both XRF and Fire Assaying.

After melting the bars and flaking them, I will test again. The average is confirmed. 
Also, out of three operations, I dried in two operations after flaking.It was acceptable.


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## nickvc (May 19, 2022)

Thank you , that’s the first steps confirmed as minimal loses or possible causes of loses.
Next you load your reaction vessel with your flake and add your acids so where do any fumes go? I’ll assume you vent them off but what to? 
If the reaction is fairly violent then any piping and the end recipient vessel could have gold solution in them , have you tested them ? A simple stannous test will confirm if you have small amounts there or larger amounts that could be some of your loses.
4metals will have a better understanding of any potential loses here rather than me as I have never used this sort of system but I think closed systems certainly have more chances of hidden loses, in pipes , filters etc , than an open one .


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## Gold.refinery (May 19, 2022)

The vapors from the reaction are transferred to a titanium condenser condensed with gas to less than 0 ° C and returned to the reactor. I can test the circulating water in scrubbers with stannous , right?

Large-scale refining, for example, 20 kg in a shift work, is done with similar devices, of course, 4 metal must confirm !!!


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## 4metals (May 19, 2022)

Gold.refinery said:


> Large-scale refining, for example, 20 kg in a shift work, is done with similar devices, of course, 4 metal must confirm !!!


The capacity of the system you purchased is based on the volume the reactor can hold. The manufacturer can tell you the volume in liters the reaction vessel can safely process. That reactor needs to hold approximately 86 liters of acid to process 20 kg per cycle. Some manufacturers are pretty slick and they realize you can push the system and process 2 runs a day so they rate the system as processing 2 lots. It is hard to tell from your system the volume the reaction vessel holds. That is something you need to ask the manufacturer. Ask them specifically what the working capacity aqua regia is in liters. 

Their volume calculation should leave room for a reaction to rise without the solution level getting too close to the exit point of the fumes because it will suck out values (as Nick cautioned) if it gets too close. 

Please post a photo of your system standing in front so I can see the distance relationship between the condenser and the exhaust port. 

I have noticed that when anyone covers multiple points in a single post, especially if they get long, some questions are not answered. To assure we get all of your issues addressed, I will use a separate post for each important issue covered.


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## 4metals (May 19, 2022)

Gold.refinery said:


> We have a Stannous test , but we do not know when to use it exactly .
> We have not seen a positive test so far.


*Stannous chloride goes bad.* And it's not the kind of thing that you can predict based on shelf life. Since you have not seen a positive test for gold thus far, alarm bells go off in my head!

What I always teach new refiners is when you test gold solutions with stannous chloride, if the first test of the day produces a negative result, you have to test the test. This is simple to do. Get a small dropping bottle that holds perhaps 50 ml and use it to store acid which will test positive. To a small beaker add a half a gram of gold and dissolve it in a small quantity of aqua regia. When it dissolves, transfer it to the dropping bottle and fill it with water. You now have a solution that will keep very long that will test positive for gold with your stannous chloride solution. 

I always like to see that dropping bottle stored right next to your stannous chloride testing solution so you will use it. What successful refiners know is that you CAN NOT tell if a solution has gold in it by looking at it. Stannous chloride is your eyes! And just like humans, you need to routinely have your eyes checked!

Please make up the test solution and test your stannous chloride. It is a small step but an important one.


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## 4metals (May 19, 2022)

nickvc said:


> If the reaction is fairly violent then any piping and the end recipient vessel could have gold solution in them , have you tested them ? A simple stannous test will confirm if you have small amounts there or larger amounts that could be some of your loses.


This is absolutely true, every refining system will trap values in exhaust ductwork, good systems keep it to a minimum. But that is not something you can change while operating a system, it is something that is minimized by design. 

The reason I asked for photo's of the front of the system is to see where your condenser is and where the fumes exit the reactor. The sooner the fumes hit the cold condenser the better it performs its job. 

The Italian. made systems use glass condensers and they are located directly above the fume exit point and drip directly back into the reaction vessel. They do not condense into a duct and run back down hill to the reactor as that will do as Nick cautioned, trap values. 

these are a few photos of the condenser and its location on the Italian system. 


here you can see the relationship between the condenser and the reaction vessel.

and here on a larger system. on both systems the glass condenser is directly above the high end of the reactor. Minimal piping connecting all condensate to the reaction.


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## nickvc (May 19, 2022)

4metals i hope you agree a step by step diagnosis of the processes should help us to help him find the areas of loses or possible ones .


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## 4metals (May 19, 2022)

Absolutely, this is why I am trying to
go through it slowly and systematically. Once we have a better idea, hopefully reinforced with photos, we can move on to the chemistry, which has room for improvement.


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## 4metals (May 19, 2022)

This is one of the smaller tumbler plants I have ever been involved with. This one has a capacity of about 6kg of karat scrap.

The reason I am showing these is because they all operate on the same principle as the plant we are discussing here, albeit from a different manufacturer. By seeing different systems we can gain a broader perspective.

Since this system is more compact it is easier to see the condenser and its location, and the filter under the reactor where the loaded solutions are filtered before being pumped to the precipitation tank. All very similar to the OP’s system. 


View attachment 6AB52EED-2F28-4C20-B68B-5BC68002868B.MOV


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## Gold.refinery (May 19, 2022)

At the earliest opportunity, I will prepare a bottle containing gold and AR to test the correctness of the stannous .

The photo shows the way of the fumes to the condenser.


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## Elemental (May 19, 2022)

This is a simple piece of advice, but have you given any thought to running a known standard through your system? (This would be a control run.) Weigh and measure our XX grams of gold, silver, PGMs, copper, iron, rock, etc. and then conduct your process to recover the gold/silver/PGMs. If you have an accurate input, let's say 100 grams of gold as input, then you can run your system and you should recover near 100 grams of gold as output. If/when you don't, work your way back through your system testing/diagnosing where the gold is getting hung up in the process.

Elemental


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## Gold.refinery (May 19, 2022)

According to previous information from the machine manufacturer, the volume of the Tumbler is 25 kg of scrap gold. 
The volume of Tumblr is more than 200 liters.


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## 4metals (May 19, 2022)

Gold.refinery said:


> According to previous information from the machine manufacturer, the volume of the Tumbler is 25 kg of scrap gold.
> The volume of Tumblr is more than 200 liters.


I think there is some B.S. going on with the manufacturer. If the tumbler was 200+ liters you would have a capacity of refining 1500 ounces or 46+ kilo's per lot. Looking at the photos of your staff leaning on the system, that guy is either a giant, or the capacity of the vessel is 200 liters upright, but at the angle it rotates the volume is at least halved. But at 100 liters working capacity you have room for 20 kg of karat and room for the reaction to rise without risk of sucking values into the condenser. 

The short length of duct connecting the tumbler vessel to the condenser is short and likely will not hold excessive quantities of dried solution. In addition The Hydrochloric acids and Nitric acids are added through that ducting as well. This will effectively rinse any condensate back towards the reactor vessel. Rinse water is also added through that pipe, I assume. This provides additional rinsing of the duct. The thin hose, I assume, connects to your dosing pump to add peroxide to the reaction. 

I am reasonably confident that you are not losing values up the stack. I hope you can rinse sufficiently to clear all of the liquids out of the tumbler and into the Silver Chloride filter beneath. Most of the silver chlorides are fine particles and the lumps which are encrusted gold are much larger. One trick I have used is to make from a 5 gallon pail (remember refiners love 5 gallon pails) a holder for polypropylene mesh paint strainers which sits on top of your filter paper and keeps the larger chunks confined and easier to collect. These photo's should help you to make one.

Cut the bottom off a 5 gallon pail and make the half circle cuts so the solution flows out freely

add one of these paint strainers made to fit on a bucket


This prescreen sits on the filter, the fine silver chlorides and all of the solution goes through easily and quickly into the filter below and the larger chunks are trapped. They can be rinsed clean into the filter and allow you to quickly collect any insolubles.

A question about your silver chloride filter. How is the paper attached to the plate of the filter? Is it by suction or by a gasket inserted into a space between the plate and the vertical wall of the filter?


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## 4metals (May 19, 2022)

Providing you rinse all of the retained solution from your filter and properly drain or rinse clear the piping leading to the tank where you will drop your gold, you will have taken the necessary precautions to assure as much of the gld laden solution is where it belongs as possible. It would be wise to test a small bit of the last of the rinse waters falling into the with stannous chloride to be sure it is negative, meaning all of the solution with gold has been rinsed clear. 

You can see you will be using a good quantity of rinse water. I suggest you do not add extra rinse water to the reactor before filtering. I would add a bag of ice cubes to cool the acid before filtering. This will lower the solubility of the silver chloride and allow more of it to be caught on the filter. The rinse waters used to assure all of the liquid holding gold should serve as the liquid you added to the vessel before filtration earlier. 

Please provide a photograph of the tank you are using for the precipitation of the gold. And from here we can address the chemistry to drop the gold.


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## Geo (May 19, 2022)

The last time we spoke about it, he had lowered the loss of gold to 9 grams total. The AgCl was collected from the same solution in one go. There is a high probability that the AgCl still contains metallic gold that was collected along with the AgCl, as he said there was a tan color in the AgCl solids. I tried to guide him to do an aqua regia wash of the AgCl but his concerns are the AgCl will dissolve in the AR and be carried away. He want's to convert the silver and cast it into anode bars and part them in a parting cell to recover the gold that way. When I was explaining to him that the parting route would take much longer than leaching in AR, that is the last time we communicated.

From the description as he described it to me, the gold could very easily be tied up in the AgCl. I can't think of any other tan powder it could be. I advised him to change the process to where he leaches the material in nitric acid to remove the silver, and any other metals nitric acid would remove, with nitric acid first before going to AR. I think there is a language barrier.


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## Geo (May 19, 2022)

Make your gold standard at 1 gram per liter. You can dilute this solution several times to get differing quantities to test against. Just testing viability of stannous chloride is simply getting a positive test result. If you practice with differing concentrations, you will learn to judge quantities of metal in solution up to the point where the test instantly goes black.


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## Lou (May 19, 2022)

This is wisdom from Geo. 

Making a series of known concentration gold lets you ball park a variety of things. Even more useful than in refining is knowing how to do this quick and dirty educated guess work in recovery.


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## 4metals (May 19, 2022)

There seems to be more going on here than we all have been told. What I do know is Gold Refinery has a commercially made refining system which is capable of refining the karat material he is planning to process. *But what he does not have is the knowledge to process the material and maximize his success.* Nor does he have an ability to figure out where his losses were or how to end them. 

Gold Refinery, you cannot expect half a dozen people to help you when you give everyone a different part of the story. The only way this can work is to keep all the information about successive lots and losses together lot by lot. Gold in Silver Chloride can be recovered, actually without much difficulty, and you were given those instructions on another thread.

You have a commercial refining system, an induction melt furnace, and some analytical capability in XRF or fire assay. And I am quite sure they came at considerable cost to you. But you cannot pull it all together if you can't focus and work this through. Nobody here on the forum will have any more or less gold tomorrow if this doesn't work out for you. You however, will have less gold. And, before long, start to question the wisdom of setting up a commercial venture without knowledge of the process. 

You could spend a lot of capital paying someone to teach you what we are trying to teach you here for free. That little tip Geo gave you about standardizing your gold standards to get a better idea of the quantities of gold you are finding will be quite useful in bringing about the success of your operation. And he offered it freely. It's about time you open your eyes and start to respect what's being given to you here. And the only price you have to pay is describing your process so we can assist you better.


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## 4metals (May 19, 2022)

Thank you Geo.


Geo said:


> Make your gold standard at 1 gram per liter. You can dilute this solution several times to get differing quantities to test against. Just testing viability of stannous chloride is simply getting a positive test result. If you practice with differing concentrations, you will learn to judge quantities of metal in solution up to the point where the test instantly goes black.


This takes stannous chloride testing to the next level, much more useful than the simple yes there is, or no there isn't, test. But it is also a technique which becomes a useful tool with practice. 

This works most effectively if you make up your test solution the same every time. Consistency will matter especially at the lower detection limits of the solution.

This is how I prefer to make the solution.

2 grams stannous chloride crystals
1 gram of tin metal
40 ml of water
5 ml of hydrochloric acid

Store this in a small air tight dropping bottle (opaque if possible) 

And remember if your first test of the day turns out negative, test the testing solution.


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## Gold.refinery (May 20, 2022)

4metals said:


> I think there is some B.S. going on with the manufacturer. If the tumbler was 200+ liters you would have a capacity of refining 1500 ounces or 46+ kilo's per lot. Looking at the photos of your staff leaning on the system, that guy is either a giant, or the capacity of the vessel is 200 liters upright, but at the angle it rotates the volume is at least halved. But at 100 liters working capacity you have room for 20 kg of karat and room for the reaction to rise without risk of sucking values into the condenser.
> 
> The short length of duct connecting the tumbler vessel to the condenser is short and likely will not hold excessive quantities of dried solution. In addition The Hydrochloric acids and Nitric acids are added through that ducting as well. This will effectively rinse any condensate back towards the reactor vessel. Rinse water is also added through that pipe, I assume. This provides additional rinsing of the duct. The thin hose, I assume, connects to your dosing pump to add peroxide to the reaction.
> 
> ...


You guessed it, acids are added from the same tube, but water is not added from there.
The silver chloride filter is a fabric. Polypropylene fabric. 
It is fixed with a washer (large ring the size of a filter).


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## Gold.refinery (May 20, 2022)

4metals said:


> Providing you rinse all of the retained solution from your filter and properly drain or rinse clear the piping leading to the tank where you will drop your gold, you will have taken the necessary precautions to assure as much of the gld laden solution is where it belongs as possible. It would be wise to test a small bit of the last of the rinse waters falling into the with stannous chloride to be sure it is negative, meaning all of the solution with gold has been rinsed clear.
> 
> You can see you will be using a good quantity of rinse water. I suggest you do not add extra rinse water to the reactor before filtering. I would add a bag of ice cubes to cool the acid before filtering. This will lower the solubility of the silver chloride and allow more of it to be caught on the filter. The rinse waters used to assure all of the liquid holding gold should serve as the liquid you added to the vessel before filtration earlier.
> 
> Please provide a photograph of the tank you are using for the precipitation of the gold. And from here we can address the chemistry to drop the gold.


 You said not to add extra water to the reactor before filtering, why? 
Instead of adding ice, we have 2 Celsius water. And add some before filtering.


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## Gold.refinery (May 20, 2022)

Geo said:


> The last time we spoke about it, he had lowered the loss of gold to 9 grams total. The AgCl was collected from the same solution in one go. There is a high probability that the AgCl still contains metallic gold that was collected along with the AgCl, as he said there was a tan color in the AgCl solids. I tried to guide him to do an aqua regia wash of the AgCl but his concerns are the AgCl will dissolve in the AR and be carried away. He want's to convert the silver and cast it into anode bars and part them in a parting cell to recover the gold that way. When I was explaining to him that the parting route would take much longer than leaching in AR, that is the last time we communicated.
> 
> From the description as he described it to me, the gold could very easily be tied up in the AgCl. I can't think of any other tan powder it could be. I advised him to change the process to where he leaches the material in nitric acid to remove the silver, and any other metals nitric acid would remove, with nitric acid first before going to AR. I think there is a language barrier.


We can not recover silver chloride with cells. We do not have cells. 
There must have been some gold trapped in our silver chloride.

*One of our most important questions:*
In the following, I will ask for help for the most suitable method of recovering trapped gold, silver from silver chloride.



Help me make *different samples* to test the tin .. !!!


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## orvi (May 20, 2022)

In big drum connected to filters, pipes and condensers, there is plenty of opportunity to lose gold. As 4metals said, half a cup of pregnant liquid will make you unacceptable losses you are experiencing. Altough this is only one of the possibilities where the gold can be. As we all suggested, follow the route of the gold, stepwise from part to part in you apparatus and rinse every part clear with water. Then test this water with stannous chloride to make sure it is gold-free.

My opinion on this is, that the loss will be a puzzle of more than one or two failures or hidden faults in the process. We already debunked incomplete precipitation/sedimentation and find around 3,5g of lost gold. That is promising thing. Now, it is time to find other faults.

From my view, there is maybe one strange question: do you wash your tumbler and filtering apparatus after every use ? or you left them as they are and proceed with another dissolution ?
If you do wash your system, gold trapped in the way will come out in washes. If you do not wash all the piping, it will stay there to the next run. This will make a huge difference in output.


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## orvi (May 20, 2022)

Gold.refinery said:


> We can not recover silver chloride with cells. We do not have cells.
> There must have been some gold trapped in our silver chloride.
> 
> *One of our most important questions:*
> ...


If the silver chloride isn´t snow-white colour, there is very high possibility gold in tumbler produced dust that is mangled in between AgCl. 
Easiest way is to dissolve AgCl in ammonia. But I must point out that for large scale this is far far from good technique to recover lost gold. You need quite a bit of ammonia to dissolve silver chloride cake.

For large scale I would advise to fully dissolve the gold. Make some AR, put it together with AgCl and let it react till there is no gold left in the cake. You can then filter the reaction and recover the impure gold, which could be added to the start of the next batch.

But as test for AgCl locked gold, it´s a very good thing to use NH3. Firstly, you need to be sure no gold solution is present in AgCl and that it is rinsed COMPLETELY from the gold solution. Do not add any water or do not use a dripping wet sludge - solubility of AgCl sharply decrease with ammonia concentration going down. 
Take a sample (like a teaspoon) to the beaker, pour few mLs of NH3 and stirr. Eventually, with slow addition of NH3 and stirring, all AgCl should enter the solution - which should be colorless, if AgCl was pure. If any gold is present in AgCl - it won´t dissolve and left as precipitate in the beaker.

If this is the case and you have leftover gold in AgCl, than i bet there will be significant portion of the lost gold percentage. Inform us how it went.


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## Gold.refinery (May 20, 2022)

4metals said:


> Thank you Geo.
> 
> This takes stannous chloride testing to the next level, much more useful than the simple yes there is, or no there isn't, test. But it is also a technique which becomes a useful tool with practice.
> 
> ...


Stannous chloride solution made by machinery manufacturer in our refinery. 
He has given us white powder. 
He dissolved 50 grams of that white powder in 2 liters of water. 
I do not know if it is true or not?


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## Gold.refinery (May 20, 2022)

orvi said:


> In big drum connected to filters, pipes and condensers, there is plenty of opportunity to lose gold. As 4metals said, half a cup of pregnant liquid will make you unacceptable losses you are experiencing. Altough this is only one of the possibilities where the gold can be. As we all suggested, follow the route of the gold, stepwise from part to part in you apparatus and rinse every part clear with water. Then test this water with stannous chloride to make sure it is gold-free.
> 
> My opinion on this is, that the loss will be a puzzle of more than one or two failures or hidden faults in the process. We already debunked incomplete precipitation/sedimentation and find around 3,5g of lost gold. That is promising thing. Now, it is time to find other faults.
> 
> ...


Because we are conducting pilot operations to gain experience, we wash the filters and paths that may contain gold each time.

We got a better result in the last operation. Approximately 6.6 grams of gold was not obtained in 2900 grams of feed. 
But we still have a lot of questions, I did not ask them to go with the 4metal way. 
Our basic information seems to be flawed.


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## orvi (May 20, 2022)

Gold.refinery said:


> Help me make *different samples* to test the tin .. !!!


I do not understand why you want to test tin, but I assume you wanted to test gold with tin (II) chloride. Correct me if I am wrong.

It is wise to take one afternoon and *get familiar with stannous chloride* test.* It´s quick, cheap, straightforward and work to quite a dilution* (good test can catch 0,1g/L gold, if trained eye is watching).

Firstly, prepare stannous chloride testing solution with recipee posted before here. Store it in airtight container - because oxygen in the air will slowly decay the solution.

For learning and "testing the stannous testing solution", it is necessary to have one standardized gold solution to prove the test is working. Remember, you will only use one drop at the time = you do not need half a liter of it 

Take 0,1 g of gold and dissolve it in AR. After completely dissolved, adjust the volume of the solution to 100 mL. Voilá, you now have 1g/L standard gold solution. I will also advise to pipette like 1mL to two separate vials, and adjust the volume to 2 mL and second to 4 mL, respectively. These will produce solutions with strength of 0,5g/L and 0,25g/L. Test these "surely gold containing" solutions with stannous test and observe the reaction. You will clearly see the strong violet-black reaction of the 1g/L solution. As the concentration goes down, colour will be more violet and below 0,25g/L slowly start to vanish. Opposed, if you test the pregnant solution straight from the reactor, you will get completely black, very dark test - because concentration is very high, far more than 1g/L.
*You need to see this with known standard solutions BEFORE you will test the real life refining solutions and rinses.*


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## orvi (May 20, 2022)

Gold.refinery said:


> Because we are conducting pilot operations to gain experience, we wash the filters and paths that may contain gold each time.
> 
> We got a better result in the last operation. Approximately 6.6 grams of gold was not obtained in 2900 grams of feed.
> But we still have a lot of questions, I did not ask them to go with the 4metal way.
> Our basic information seems to be flawed.


I am happy to hear that your operation is improving. We will slowly work it out. Gold cannot hide, it´s there somewhere, waiting to be found


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## orvi (May 20, 2022)

Gold.refinery said:


> Stannous chloride solution made by machinery manufacturer in our refinery.
> He has given us white powder.
> He dissolved 50 grams of that white powder in 2 liters of water.
> I do not know if it is true or not?


White powder will probably be solid stannous chloride dihydrate. This compound isn´t the most stable compound ever - it slowly hydrolyses and emmit HCL, transforming to hydrated tin oxides. But it takes some time.
I will ask for fresh batch, and test it with standard gold solution described above. If it give you dark violet-black colour, it´s a good testing solution. If the result will be faint violet or no reaction, abandon this "white powder" and make your own one


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## Gold.refinery (May 20, 2022)

orvi said:


> If the silver chloride isn´t snow-white colour, there is very high possibility gold in tumbler produced dust that is mangled in between AgCl.
> Easiest way is to dissolve AgCl in ammonia. But I must point out that for large scale this is far far from good technique to recover lost gold. You need quite a bit of ammonia to dissolve silver chloride cake.
> 
> For large scale I would advise to fully dissolve the gold. Make some AR, put it together with AgCl and let it react till there is no gold left in the cake. You can then filter the reaction and recover the impure gold, which could be added to the start of the next batch.
> ...


To recover gold trapped in silver chloride, I am looking for a large-scale method, I hate ammonia very, very much. Each method must be such that it can be used many times, not just once.

to drop a large amount of silver chloride into the AR, then filter the solution and take the gold.It seems good. Do other people agree?


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## Geo (May 20, 2022)

Prepare your gold standard first. It should be on hand. 4metals gave you the formula to make your stannous chloride.

2 grams stannous chloride crystals
1 gram of tin metal
40 ml of water
5 ml of hydrochloric acid

All of these ingredients for 40ml's of solution. The formula that you gave has roughly half the weight of stannous chloride crystals per same volume of solution than what 4metals gave. I would say that it would be insufficient. 
Once you have you test solution and gold standard, then you will no longer be refining in the dark. 
Threat the silver chloride with hot AR to dissolve any wayward gold. Filter the silver chloride and rinse well. Denoxx and precipitate any gold from solution. 
In between here and there, some AgCl may dissolve. It will be very little over all. If you allow the solution to cool completely and then chill the solution, nearly all of the silver will precipitate as AgCl again. By the time you filter, there should only be a trace of silver chloride left and that will filter out. There's nothing to it more than that. If the solution contains no gold, you can rule the AgCl completely out. If the lost gold is there, you can figure out how to change some thing to stop the gold getting trapped with the silver.


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## 4metals (May 20, 2022)

Gold.refinery said:


> Stannous chloride solution made by machinery manufacturer in our refinery.
> He has given us white powder.
> He dissolved 50 grams of that white powder in 2 liters of water.
> I do not know if it is true or not?


Making the stannous chloride up 2 liters at a time is just too much to have prepared and inviting it to go bad. 

The formula I gave you, one of many that work, is made up to a volume of 45 milliliters. When you test with stannous chloride you use one drop to test. So the 45 ml as I suggest will give you about 900 tests. That will last you for a while. The 2 liters will give you 40,000 tests! It will go bad by the time you have used it up. 

If you notice the formula I prefer has metallic tin and hydrochloric acid. While the powder you have (assuming it is stannous chloride) will produce a stannous chloride solution, there is little done in the way of preserving the solution for longevity. 

Tin chloride has a stannous form and a stannic form, stannous works for us and stannic doesn't. Aqueous solutions of stannous chloride undergo hydrolysis which is why they go bad. The tin added to the solution helps prevent this oxidation. So the addition of the Hydrochloric Acid and the Tin metal acts as a preservative. 

Another trick useful for stannous testing is useful for dirty solutions. Often with low concentrations of gold in solution, a dirty solution being tested will mask the result. To help overcome this, place a few drops of the dirty solution on a paper towel and a few centimeters away place a drop of your stannous chloride testing solution. The paper towel will wick the liquids outward and any particulate in the dirty sample will remain behind as clearer solution migrates outward. By placing the drops a few cm apart, they will merge as cleaner solutions and when they touch, usually in less than a minute, the reaction is easier to see. Just focus on the leading edge of the migrating liquids and look for the reaction to indicate the presence of gold. You are likely to encounter dirtier solutions if you start testing your cemented solutions so it's a good trick to keep in mind.


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## 4metals (May 20, 2022)

Discolored Silver Chloride can be from other things like exposure to light. Generally there are 2 things to look for in the silver chlorides on the filter. First and foremost the chunks. If you make the prescreen I described earlier those chunks will be easy to rinse and collect leaving you with the fines of Silver Chloride which are sitting on the filter paper. These chlorides can also contain gold but usually it is low enough to collect the chlorides and process them in bulk. 

In a production environment it is typical to look for a recovery of 99.75% or better. If you get that you can assume the balance is in the chlorides and collect your chlorides for recovery later. I am not a big fan of ammonia for dissolving chlorides either. I would go with either the caustic sugar route or reducing with iron. Either way it is better to accumulate them if your yields after considering the gold content recovered from the process plus the gold content by assay in any chunks removed from the Silver Chloride and cleaned and melted into a button for assay, is up to your expected yield. (99.75%)


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## 4metals (May 20, 2022)

Gold.refinery said:


> to drop a large amount of silver chloride into the AR, then filter the solution and take the gold.It seems good. Do other people agree?


You are trying to dissolve the gold that was trapped in the silver chloride on your first attempt with the same acid that trapped it the first time without doing anything to release the gold trapped. The silver chloride is not soluble in aqua regia so this method will not work. 

I suggest either the caustic sugar approach or the iron reduction. Either will work. Either will produce silver metal which can be dissolved in nitric acid to release the trapped gold. Once filtering out the gold, you can drop the silver again with Hydrochloric Acid or salt and filter out the white fluffy silver chlorides. These can be well rinsed and reduced to high purity Silver using the caustic and sugar method with a lot of rinsing. 

The first reduction will produce metallic Silver which can be dissolved to collect the remaining gold from the karat dissolve. The second dissolve will yield Silver Chloride which the caustic sugar method can be used to give you a saleable Silver.


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## 4metals (May 20, 2022)

Gold.refinery said:


> You guessed it, acids are added from the same tube, but water is not added from there.


Some of the systems add water through that duct as well as acids. It can be problematic because you cannot see into reaction vessel and you may add too much.


Gold.refinery said:


> You said not to add extra water to the reactor before filtering, why?
> Instead of adding ice, we have 2 Celsius water. And add some before filtering.


The goal here is to get the solution as cold as you can to keep the silver out of solution. Your method has you adding a prescribed volume of water which cuts your acid (and gold) concentration in half. Ice will accomplish the cooling without the volume.

The reason I do not suggest adding too much water is you will be adding water to rinse out all of the reactor and pipes as well as the filter so you will end up with a lot of waste to deal with. The ice does the job cooling the liquid. I would next be filtering the cooled acid and then rinsing the reactor clear.

The spinning reactor has a large port on the cylinder which is opposite the drain port. Once the iced liquid has been filtered, remove that cover, rinse the acid on the inside of that cover into the reactor, and look straight down to the drain port on the opposite side of the reactor. You will see a crescent shaped pool of acid that is concentrated acid, with gold. This is because it is near impossible to fabricate the drain exactly at the bottom of the vessel to drain completely and the space between the drain hole and the bottom sitting at the angle of the rotating vessel, creates the small crescent shaped pool I described. Rinse that pool of acid until it is clear and using a wand you make to spray inside the reactor, use water to rinse the inside of the reactor completely. This will assure you have gotten all of the values into the filter below. This should also use less water than a 50% dilution with cold water followed by a rinse. For waste treatment later this will be important.

From here rinse the filter holding the silver chlorides until it tests negative for gold and pump the filter dry. When you remove the filter media to collect the chlorides, open the top of the filter and make sure all of the surfaces are rinsed through the pump.

Now we are of the assumption that all of the values, except those tied up in the chlorides, are in your precipitation tank and are ready for your precipitation.

Please send a photo of the tank you use for precipitation and describe the method you are currently using to drop the gold.


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## Gold.refinery (May 21, 2022)

We have 3 of these tanks.
The first tank is for precipitation of gold. 
Then the mother solution is transferred to the second tank after the gold is filtered (here the gold remains on the filter). 
It stays there overnight and then filtered into the third tank (here the sludge contains copper and the rest of the gold left over from the previous stage).

Each tank consists of two valves, one at a height of 17 cm, one at a height of 7 cm from the floor) The second fir little solution). 
There is also a big valve on the bottom of the tank for final washing.

A tube with air flow is used manually to completely dissolve the solution and mix it.


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## nickvc (May 22, 2022)

If the OP had only done one process then any solution trapped in the reaction vessel could explain his lose but I believe he has done three all with similar loses on each one , so to my mind if there are no lose to the fume extraction then it would logically be from filtering onwards.
We know there is some gold trapped with the silver chlorides and in the settlement tanks and I suspect because he is dropping everything that the main lose might well be hidden there amongst all the base metals, how is that material been assayed as if it’s by xrf it may well be wrong.


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## Gold.refinery (May 22, 2022)

nickvc said:


> If the OP had only done one process then any solution trapped in the reaction vessel could explain his lose but I believe he has done three all with similar loses on each one , so to my mind if there are no lose to the fume extraction then it would logically be from filtering onwards.
> We know there is some gold trapped with the silver chlorides and in the settlement tanks and I suspect because he is dropping everything that the main lose might well be hidden there amongst all the base metals, how is that material been assayed as if it’s by xrf it may well be wrong.


Our losses have not been the same in three operations. The first operation is 27 grams out of 2700 grams (by accident), the second operation is 12.6 by 2610 grams and the third operation is 6.6 by 2900 grams. I can explain the differences of each operation, we added the sludge from the second operation to the feed of the third operation. 
I agree with you about concentration on Filters. 
You guess most of the gold is lost in the base metals, is this because of our use of hydrazine for sedimentation ?? 

I did not understand what you meant about our wrong analysis with XRF.


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## 4metals (May 22, 2022)

I think filtration here is a big part of the issue. First thing is there are a good number of manufacturers selling tumbler systems and from my experience they provide the equipment, provide a poorly written description of its operation, and pretty much leave the proud new owners of the equipment on their own. 
I do not understand why, after using the filter to filter the dissolved alloy in the tumbler, they feel there is a need for an in line filter. You either filter properly or you don't. On thinking about this, and going back over the photo's, and what I know first hand about other tumbler systems, there are a few things amiss. 
In this photo provided by the OP, the grid on the bottom of the filter has some rather large openings. 
The OP has said they use a reusable fabric filter on this filter. He did say the filter is held in place with a gasket so I assume nothing leaks around the filter. But from what I know about these filters, if the openings are too large, as these are, there is a necessity to put a fabric over the grid to prevent any filter sheets from sucking into the holes. I believe the screening the OP is using is intended to support the proper filter papers placed on top of the reusable screen. And by not using any filter media other than that screen, silver chlorides will definitely pass through the filter. What is the mesh size of this reusable screen can Gold Refinery provide us with that information, and possibly a close up photo of the screen? If the filter is working as intended it should not require a downstream spiral wound cylindrical filter. 

Secondly, they drop the gold in one of the tanks, again filter it, and then store it in another tank to, as Gold Refinery put it


Gold.refinery said:


> The first tank is for precipitation of gold.
> Then the mother solution is transferred to the second tank after the gold is filtered (here the gold remains on the filter).
> It stays there overnight and then filtered into the third tank (here the sludge contains copper and the rest of the gold left over from the previous stage).


Again, if the filtration is proper, the gold precipitates should be in the filter, not beyond. A well designed refining plant puts all of your values (within reason) in one place and shouldn't leave the refiner chasing all over the process equipment looking for lost values. Gold Refinery, a close up photo of the grid on the filter and of the reusable screen you place on top, I think this is an issue we need to correct.



Gold.refinery said:


> A tube with air flow is used manually to completely dissolve the solution and mix it.


Bubbling air is not an effective mixer with something as dense as gold. It's great to move solutions but when precipitating gold there is something that happens when you drop a lot of gold that most do not realize. When you have the air bubbling and start dropping your gold, as the gold drops, it is blanketing the bottom and actually remaining surrounded by gold in solution that becomes trapped under a few inches of precipitated gold mud. Since a column of air bubbles will not effectively lift the gold off the bottom, the solution mixed and trapped under the precipitated gold can not react. You finish adding your precipitant, test with stannous, and assume all of the gold is dropped. Except there is gold in the solution trapped by the gold sponge that has not been properly exposed to the chemistry you are using. Remember we discussed just how much gold a small quantity of aqua regia can hold, this can be significant in your case.

The fix to this is to physically use a wide blade paddle to physically move the gold sponge you have precipitated and allow that solution to also react and drop its gold. Most systems have a large blade mixing motor to assure good movement of the gold as it drops and keep it moving to avoid this issue. Your air bubbler will not accomplish this. 

When you transfer to the next tank, that solution which still has gold in solution, reacts with the chemistry and drops out. It can pass through a filter when it is dissolved but will drop in the solution it is mixed with in the next tank. Possibly that is why there is a second tank. To use an a
American phrase, that is Mickey Mouse! To fix it, agitate properly to assure complete precipitation and filter it properly and it will all be where you expect it, in the filter. 

Everything we have touched on thus far reflect on the operation of the physical equipment, not your choice of chemistry. Send photos of the grid and the screen to help figure this out.



Gold.refinery said:


> I did not understand what you meant about our wrong analysis with XRF.


XRF is often mistaken on sludges or powders and without proper sample preparation and the proper algorithm running on the software, the answer spit out by the same XRF you used to analyze the karat scrap is not to be believed.


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## 4metals (May 22, 2022)

These are images from another system. This is the smallest system I have ever worked with, I have photos of larger ones but these will suffice as an example. This is the tank where the gold is dropped and it is filtered. Basically they are all simply raised tanks which allow a filter to fit beneath. They usually have a slightly coned bottom to allow complete drainage, and some type of effective mixing. The photo on the top left shows the gold rinsed and sucked dry on removal from the tank, to it's right is the tank with the filter seen below. The next photo is just the system at another angle, and the last shows the mixer blade which is permanently fixed in the tank.


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## 4metals (May 22, 2022)

This is another photo of a filter showing the removable grid and the tools to remove the grid. The 2 circles sticking up are supplied to fit into slots made to simplify lifting out the plate to rinse it completely. These holes are 5 or 6 mm in diameter, smaller than in the grid shown by the OP. This manufacturer supplies 2 grades of filter paper, the heavier is rather rigid like thin cardboard and it does not necessitate using a reusable screen below it, the thinner paper is actually what most consider filter paper. Without a screen mesh below it to support it, it will be punctured by the vacuum and allow solution (and solids) through.





compare these holes to the holes in the OP's filter.


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## orvi (May 22, 2022)

Point with poor mixing during the drop is very concerning. I will definitely try to check that and stirr manually, if there is not any overhead stirrer available. Also, gold powder in thick layer is hard to stirr with lower power stirrers. It tend to collect around the walls and stay there.

It will be then easy to check the solution that passed filter for any soluble gold. 5 g in 25 liters is detectable with stannous without much problems.


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## 4metals (May 22, 2022)

orvi said:


> It will be then easy to check the solution that passed filter for any soluble gold. 5 g in 25 liters is detectable with stannous without much problems.


In a perfect world, absolutely true about the sensitivity of stannous chloride. But the circumstances here are different. Let's say enough liquid containing gold was trapped under the gold sponge to hold some gold. The solution mixing above it will test negative so you might not even realize it is there. If you use a paddle to mix it up, the time between the solution being trapped and the solution being exposed to the liquid above, likely with enough chemistry to reduce the newly exposed gold, will often drop the gold quickly. So even stirring will not indicate it. 

if you didn't stir it, or stirred it inadequately, the liquid gold would go through the filter and the rest of the solution and reducing agent will follow behind, reducing it to metallic gold where it will not be indicated by stannous and settle to the bottom. (along with any other crap on the bottom)

So this system makes it difficult to actually prove the gold was there easily but by design it is inherent. The cure is adequate mixing. 

The reason I said most don't realize this phenomenon is because it is possible only when dropping a lot of gold so the dropped gold forms a dense thick layer in the vessel trapping pregnant solution beneath it. Few of our members deal with these quantities of gold to ever notice it.


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## Gold.refinery (May 22, 2022)

*You point out the problems carefully, thank you. But according to our conditions and the design of our device, please also provide the best solution available.*

I agree that the person who sells the device does not provide the proper training and may not be able to provide it.

From the last operation, we use two filters at the same time, a fabric filter on the lower grid with the rim fixed, and a paper filter on the fabric filter. With this technique, we got better results from previous operations. 

*Can you provide us with the specifications of a suitable paper filter? (Due to the problems of our filtration system compared to italimpant)*

The manufacturer of the device explained the reason for using the cylinder filter to better filter silver chloride, but if it wants to cause a problem, it can be removed from the way.

*I do not know the size of the fabric filter mesh.*

You said that silver chloride passes through a fabric filter. If it is filtered correctly, there is no need for a cylindrical filter.

You do not need a second bunker to filter gold if it is filtered properly.

I agree that values should be *concentrated in one place*, not several places. One place but correct. Not a few unsafe places

I will send photos and videos of the filter, network, fabric tomorrow.


Due to the lack of a suitable mixer, the amount of gold-containing solution is trapped under the deposited gold sludge and prevents the precipitator from reaching. The bubble does not work. Only physical displacement. *What is the best solution to this problem with our tank conditions?*

I noticed that the sludge and powder test with XRF is faulty. For two reasons: software standard, heterogeneous sample.


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## Gold.refinery (May 22, 2022)

We have already learned how to calculate the amount of acids from you. 
But we add the ingredients to the end, including: *water, urea, precipitate, flocculant, aluminum*,…. 

*What will be the ratio of these substances to the raw food?* 

Knowing these ratios removes the operator from doubt. 
*Seeing reactions and recognizing the amount of material is difficult for a beginner. (No experience)*


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## orvi (May 22, 2022)

Gold.refinery said:


> *You point out the problems carefully, thank you. But according to our conditions and the design of our device, please also provide the best solution available.*
> 
> I agree that the person who sells the device does not provide the proper training and may not be able to provide it.
> 
> ...


Solution to the mixing problem will be mechanical mixing (manually with some plastic paddle). You only need to stir it to the point when all liquid gold is reduced (negative stannous). Then you can leave it as is to settle down properly. But you need to know that all of the gold is out of solution - this is the time when stannous chloride will become handy as a proof your solution AFTER STIRRING WELL do not contain any detectable gold. Then you can leave it to settle.


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## 4metals (May 22, 2022)

Gold.refinery said:


> From the last operation, we use two filters at the same time, a fabric filter on the lower grid with the rim fixed, and a paper filter on the fabric filter. With this technique, we got better results from previous operations.


The paper filter needs to sit directly on the fabric filter and both need to be held in place by the rim. If the paper sits loosely on top of the fabric screen it is easy for solution to go around the edge and pass through the more porous fabric screen easily. The vacuum will not be capable of making a tight seal. Use the rim to seal both the paper and the fabric screen. 

As far as what filter media to use, first you need to know the inside diamater of the filter. Something like 50cm but this is a guess. You will need to measure it. Since you are in the UK maybe some members closer to you can recommend paper that is easier to purchase. Preferably with a porosity under 2.5 microns. 



Gold.refinery said:


> You said that silver chloride passes through a fabric filter. If it is filtered correctly, there is no need for a cylindrical filter.


This is true. If you feel you can clean the filter of all color from the solution by rinsing it can easily be tested with stannous. If it holds liquid that tests positive for gold I would remove it. If the filter shows excessive amounts of silver chloride your main filter is not performing properly. 


Gold.refinery said:


> I will send photos and videos of the filter, network, fabric tomorrow.


This will be useful as a picture speaks more than words. 



Gold.refinery said:


> Due to the lack of a suitable mixer, the amount of gold-containing solution is trapped under the deposited gold sludge and prevents the precipitator from reaching. The bubble does not work. Only physical displacement. *What is the best solution to this problem with our tank conditions?*


After you have added enough precipitant to drop the gold remove the air wand so you can access the bottom with a flat paddle made of plastic so you can feel the bottom and scrape in a circular motion until you can feel all of the gold sponge moving and allowing the liquids to mix. Allow it to settle, retest with stannous. There is a good possibility the excess precipitant already in solution has dropped the gold and it will not indicate gold in solution. If it does add more precipitant, stir again, and retest. Basically you want to make sure all of the solution trapped under the gold sponge is brought into contact with fresh solution with enough precipitant to drop all of the gold.


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## Gold.refinery (May 22, 2022)

Now that we have this point, I would like to mention some of *our important questions*: 

The capacity of our device is 25 kg.
As you mentioned, most people did not encounter this amount of material, there are different issues in *large volumes*.

*Questions*:

1)it is difficult me to add acid step by step and get Pregnant solution 5 kg , 5 kg,…
or can it be done all at once? 

2)How to calculate chemical values, especially the *amount of precipitate*. It seems to be determined on the basis of certain values by the chemist, rather than with experimental values *to see* the reactions. Seeing reactions is skeptical. 

As you know, pure gold powder has a large volume, for example, 10 kg of pure gold powder is very bulky and inflated.

3)What is the best solution for *washing* large volumes of powder? 

4)What is the best solution *to dry large volumes* of gold powder?


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## Gold.refinery (May 22, 2022)

Should we use two types of paper filters to get *silver chloride* and get *gold* powder? 

You said with a mesh less than 2.5 microns. 
Is this for both ?


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## 4metals (May 22, 2022)

If you wanted to completely eliminate the possibility of pregnant solution remaining under the gold there is one more step you can take. A client of mine in Ohio had a large cementation tank and the hole that lead to the drain valve actually held about 1 liter of liquid. (a rather large cementation tank) Based on the fact that his average assay was about 50% that meant his liquid retained in that hole was about 3.75 ounces. Assuming he rinsed his system to purge it well let's guesstimate he cut the concentration in half. Still he held 1.875 ounces or $3,300 at todays prices. That could not stand. 

On to your system, this is what sits in the bottom of your tank. (blown up from your photo)

depending on how deep that hole goes before the ball valve, you may have similar issues. The way we fixed it was to machine from PVC solid rod a tight fitting plug that went all the way down to the ball valve so no solution could fill the hole and it extended up above the solution level so it could be easily extracted after the solution was ready for transfer to the filter. Even though he did have a motor mixer, the liquid in that hole seemed to mix poorly. His standard procedure was (is) insert the plug while the tank is empty and dry, pump in the acid for recovery, drop the gold and test the solution, remove the plug, and drain the solution and the gold sponge into the filter. 

This may seem like overkill but everybody defines overkill a bit differently.


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## 4metals (May 22, 2022)

Gold.refinery said:


> We have already learned how to calculate the amount of acids from you.
> But we add the ingredients to the end, including: *water, urea, precipitate, flocculant, aluminum*,….


It seems we are now getting onto the chemical process. I have covered water in that I would add ice to cool the reaction and no water, then filter the cold solution and rinse the reactor and all of the piping and filter as well as the filter base. This will accomplish your water addition and dilution.

You are now sitting with a well filtered solution ready for the next steps.

There are better options than urea but urea is widely used and may be more available to you. This is where I fully hope other members will offer chemical solutions to put out the fullest diversity possible. Have no fear before this is over we will have debated this to give you the best, by consensus, the forum can offer. 

You Sir, have not really detailed your precipitant, your flocculant, or your logic in using aluminum. All of these will be discussed in detail once you give us your current methods. 



Gold.refinery said:


> *What will be the ratio of these substances to the raw food?*
> 
> Knowing these ratios removes the operator from doubt.
> *Seeing reactions and recognizing the amount of material is difficult for a beginner. (No experience)*


First I assume you mean feed not food. 

I firmly believe refining is as much science as it is art, and as such, it is a skill that gets better with practice. Determining the ratios is dependant on issues beyond your control and there is a point where the operator will learn to see by experience when a reaction is complete. And then follow it up with testing as described earlier. 

An operator will always have doubt, a refiner will develop his skills and awareness to the point where there is no doubt. 

So, please post your chemistry and let the chemical discussion begin.


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## Gold.refinery (May 22, 2022)

4metals said:


> If you wanted to completely eliminate the possibility of pregnant solution remaining under the gold there is one more step you can take. A client of mine in Ohio had a large cementation tank and the hole that lead to the drain valve actually held about 1 liter of liquid. (a rather large cementation tank) Based on the fact that his average assay was about 50% that meant his liquid retained in that hole was about 3.75 ounces. Assuming he rinsed his system to purge it well let's guesstimate he cut the concentration in half. Still he held 1.875 ounces or $3,300 at todays prices. That could not stand.
> 
> On to your system, this is what sits in the bottom of your tank. (blown up from your photo)
> View attachment 50265
> ...


Unfortunately I could not figure out your solution for the tank floor valve.


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## 4metals (May 22, 2022)

Gold.refinery said:


> Should we use two types of paper filters to get *silver chloride* and get *gold* powder?
> 
> You said with a mesh less than 2.5 microns.
> Is this for both ?


Yes you can use the same papers for both gold and chlorides. Some papers have a greater wet strength and make filtering gold easier as they can be rolled up with the gold inside to melt them. That is something you will have to decide based on availability.


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## 4metals (May 22, 2022)

Gold.refinery said:


> Unfortunately I could not figure out your solution for the tank floor valve.


I thought I was clear, perhaps someone else can state it more clearly. Or if my description is that far off I'll try again, just say so.


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## orvi (May 22, 2022)

If you are able to get nitric acid in bulk, you are also able to get sulfamic acid. Urea also work, but I think most of us agree that sulfamic acid performs better. Get some. You do not need much, few kilograms for next batches, you test the performance and decide what to use.


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## orvi (May 22, 2022)

Gold.refinery said:


> Unfortunately I could not figure out your solution for the tank floor valve.


4metals meant that if dropping gold, gold dust can fill the drain tube in the bottom of the tank. So no matter how well you stirr, some precipitate will always be there, undisturbed - and with possible undropped gold between the gold particles, you can easily loose them when opening the valve.

Their solution was to insert a piece of sealed plastic tube into the draining hole to prevent anything to falling down - so no liquid gold can be trapped between already settled gold particles. When the drop of all gold from liquid is confirmed, yo can unplug the bottom and drain the suspension onto the filter.


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## Gold.refinery (May 22, 2022)

In the last operation, we had scrap gold input with analysis of 
Au749, Ag60, Ni6, Cu160, Cd8, Zn11 and… .. 
2900 gr


We calculated 2.5 liters of nitric acid, 10 liters of hydrochloric acid. 
First, We added 8 liters of hydrochloric acid and 2 liters of nitric acid. After one hour, we added 3 liters of hydrochloric acid and 0.5 liters of nitric acid. After 4:30 hours, the solution had almost no reaction. Then we added about 1000 grams of urea. We had no ice. We added 5 liters of water at 2 degrees Celsius. Then we filtered the solution. 
22 grams of gold was left to dissolve. 

After washing the reactor and pipes, the volume of the solution reached approximately 45 liters. 
To precipitate gold, we dissolved 2 liters of 55% hydrazine with 2 liters of water. 
We added the solution step by step in 30 minutes. Mix well after each addition. We did not react when we added it again. 
*I think we added too much because we were not sure.*
We left the solution for 12 hours. 

We did a stannous chloride test, it was negative. (Must be control later)
We filtered the solution with two paper and fabric filters. Gold remained on the paper filter, we tested with XRF, it showed gold 997/1000 and some basic metals, most of which was *2/1000 copper*. 
We tested the mother solution with stannous chloride, it was negative. 
We added some aluminum plate to the mother solution. On the advice of the machine manufacturer, we used a solution of ammonia and water to wash the gold powder (*I hate it And I will not repeat*). 
Put gold powder in ammonia solution for 30 minutes. We then transferred the resulting washed ammonia to the mother solution (unfortunately). 
Finally in gold powder 999.2 / 1000 Au and 0.8 silver (sometimes 0.2 copper). 
Our lost gold after the calculations was 6.6 grams. 
after a day, no sludge had settled to the bottom of the mother's solution tank. After another day, we added some aluminum to the doublet, this time after filtering the solution, the sludge had accumulated, but its gold content was very small, 1.5 / 1000. Of course, 

X-ray tests do not seem correct according to your description.


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## 4metals (May 22, 2022)

Gold.refinery said:


> it is difficult me to add acid step by step and get Pregnant solution 5 kg , 5 kg,…
> or can it be done all at once?


Do the math for the addition for the entire lot. Add the shot to the tumbler. Add all of the Hydrochloric Acid and about 1/3 of the calculated Nitric Acid. When the reaction subsides add another 1/3 of nitric followed by the final 1/3 after the reaction subsides between additions.
I am used to glass condensers which allow you to see when the reaction is actively blowing red indicating a reaction. Is there any place where you can see the fume coming off the reaction?


Gold.refinery said:


> )How to calculate chemical values, especially the *amount of precipitate*. It seems to be determined on the basis of certain values by the chemist, rather than with experimental values *to see* the reactions. Seeing reactions is skeptical.


Precipitants are best added by seeing the reaction rather than just shoveling in a prescribed quantity. With karat scrap I can actually see the color of the acid and know when the drop is done. That takes practice but you always have stannous which is definite. Seeing reactions is not skepticism, it’s refining!

You will realize in a production environment that you do not have the luxury of adding a precipitant and waiting overnight for it all to drop. Manual additions will allow you to learn to drop it quickly and completely and not wait for the next day to filter, rinse and melt. 



Gold.refinery said:


> What is the best solution for *washing* large volumes of powder?


If the drop was done properly my first choice would be hot water.



Gold.refinery said:


> What is the best solution *to dry large volumes* of gold powder?


You can leave the well rinsed gold in the funnel with the suction on and it will dry it sufficiently to allow you to melt it. You can melt damp gold in the furnace but you cannot add damp gold to a molten pool of metal or it will explode from steam. Messy and costly. Fill the crucible cold with gold sponge that is not dripping but just damp. As it heats it will shrink and steam will pass off harmlessly. Keep feeding in more before it gets molten and remember if it melts don’t add any more for that melt.


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## silver1 (May 22, 2022)

So you are looking for 9 grams out of a 2,000 gram yield? That's like well over 99.5% yield accountability on the first run. You stated that this wasn't economical? I'm not chasing 9 grams on a 2,000 gram yield on the first run. That's well within my accountability rules. Catch it down stream! Sounds like steping over dollar bills to pick up dimes to me. My opinion.


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## silver1 (May 22, 2022)

4metals said:


> Do the math for the addition for the entire lot. Add the shot to the tumbler. Add all of the Hydrochloric Acid and about 1/3 of the calculated Nitric Acid. When the reaction subsides add another 1/3 of nitric followed by the final 1/3 after the reaction subsides between additions.
> I am used to glass condensers which allow you to see when the reaction is actively blowing red indicating a reaction. Is there any place where you can see the fume coming off the reaction?



*I bought some borosilicate glass tubing and added a 6 in piece inline past the reaction vessel so i can do just that.*


4metals said:


> Precipitants are best added by seeing the reaction rather than just shoveling in a prescribed quantity. With karat scrap I can actually see the color of the acid and know when the drop is done. That takes practice but you always have stannous which is definite. Seeing reactions is not skepticism, it’s refining!



*Another example of refining being an art. Most of my calculations are based on experience and wisdom rather than actual calculations. I use calculation just to get me into the ball park then i switch from auto pilot to manual flight.*


4metals said:


> You will realize in a production environment that you do not have the luxury of adding a precipitant and waiting overnight for it all to drop. Manual additions will allow you to learn to drop it quickly and completely and not wait for the next day to filter, rinse and melt.
> 
> 
> If the drop was done properly my first choice would be hot water.
> ...


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## FrugalRefiner (May 22, 2022)

Gold.refinery said:


> On the advice of the machine manufacturer, we used a solution of ammonia and water to wash the gold powder (*I hate it And I will not repeat*).


One of our past moderators always used an ammonia wash on his precipitated gold. He dropped his gold from very concentrated solutions, which can hold a bit of silver chloride in solution. He used ice to cool the solution as he added his precipitant. So, he ended up with a bit of silver chloride precipitating with his gold as the solution was diluted and cooled by the ice. He used an ammonia wash do dissolve the silver chloride before melting his gold.

Another former moderator chose to dilute his pregnant solution to three times the volume. The dilution would cause the silver chloride to precipitate, and he would filter it out before dropping his gold. It creates more waste, but he didn't need an ammonia wash.

Since you did an ammonia wash, I'm a little surprised you still had that much silver.

Dave


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## 4metals (May 22, 2022)

The 2 most common contaminants from refining karat gold scrap are silver and copper. The silver has carried over as silver chloride. The copper is usually copper chloride resulting from overuse of your reducing agent and dropping copper. 

Harold had posted his method for getting gold clean but I cannot seem to find it to post here. His lots though were not of the size the OP is processing.

The copper chloride can be rinsed free with Hydrochloric Acid and the Silver Chloride with ammonia. But large lots are not conducive to leaching out impurities because it is difficult to contact all of the metals contaminating the sponge without tumbling the sponge in the chemistry. A funnel full of gold will experience channeling and limit your ability to leach out impurities. The best bet is to eliminate the copper by not overdoing it while reducing the gold and eliminate silver chloride with good filtration of cold acids.

Without some tricks with chelating agents, getting .9999 gold in a single pass is beyond the capabilities of these systems.


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## silver1 (May 22, 2022)

4metals said:


> Harold had posted his method for getting gold clean but I cannot seem to find it to post here. His lots though were not of the size the OP is processing.











Getting pure gold (shining)


Hello, I would like to know what I must add/change to a standard AR process to get pure gold after melting it. Most of the gold buttons I get are not completly shining and seem to have a very thin layer of impurties. How can I correct that ? Thanks




goldrefiningforum.com


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## Gold.refinery (May 23, 2022)

4metals said:


> Do the math for the addition for the entire lot. Add the shot to the tumbler. Add all of the Hydrochloric Acid and about 1/3 of the calculated Nitric Acid. When the reaction subsides add another 1/3 of nitric followed by the final 1/3 after the reaction subsides between additions.
> I am used to glass condensers which allow you to see when the reaction is actively blowing red indicating a reaction. Is there any place where you can see the fume coming off the reaction?
> 
> Precipitants are best added by seeing the reaction rather than just shoveling in a prescribed quantity. With karat scrap I can actually see the color of the acid and know when the drop is done. That takes practice but you always have stannous which is definite. Seeing reactions is not skepticism, it’s refining!
> ...


There are two circles at the top of the reactor where we can see the reaction.

You recommend, for example, for 15 kg of scrap that requires 15 liters of nitric, add 5 liters, after calming 5 liters, and finally the final 5 liters. 
Doesn't that cause more unresolved gold? 

other way ; Can we just add hydrochloric acid and nitric acid for only 1/3 of the total scrap, then *filter the solution*, then add 1/3 of the total acid and so on.

During the first 20 to 40 minutes of the acid reaction, we always have some *white fume *(with a low chlorine odor) in the chimneys after the scrubber.After the peak of the reaction, it ends.

This is not a good thing, from the neighbors' point of view.Of course, no one has objected so far.

Regarding the amount of precipitate, of course we see the reaction, but *knowing the amount *of material will help. Due to the toxicity of the precipitate and the health hazards, we do not like to see the reaction too often. Produces gas during settling.

Please explain more about the color change of the solution at this stage. 

In the case of the stannous test, a few minutes after the end of the deposition reaction, we take a small amount of solution from the top of the tank to test, is this correct?

Your opinion is that if the gold deposit is done with experience and confidence, there is no need to leave the solution overnight, which is great for the production process. it's true?

In the case of washing powders, if we wash them with hot water, for example 5 times, will the *copper chloride* and the remaining base metal salts be washed ?? 
Also, washing several times *causes gold to escape or not*?

In the case of drying, in the last operation, we left it on the filter for 30 minutes, it dried a little, but it was not desirable. 
I did not notice the drying of a large volume of gold sponge in the funnel.

I know that it is not problem to melt wet powder in a cold crucible, but the volume of our crucible is 5 kg and it is cold for the first time, then it is poured.


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## Gold.refinery (May 23, 2022)

4metals said:


> The 2 most common contaminants from refining karat gold scrap are silver and copper. The silver has carried over as silver chloride. The copper is usually copper chloride resulting from overuse of your reducing agent and dropping copper.
> 
> Harold had posted his method for getting gold clean but I cannot seem to find it to post here. His lots though were not of the size the OP is processing.
> 
> ...


Exactly, silver and copper were the biggest pollutants. We need 999 and 995 carats to sell products. Focusing on the subject of washing (copper and silver) is related to the unfavorable surface of the gold ingot after the final melting. To solve this problem, we were advised to wash the gold powder better. it's true?

I added a lot of water in one operation. According to *Frugal refiner*, I do not think we had silver in the gold powder.
But in the last operation, I made the solution with more concentration and we had silver in end. 

*If we filter the silver chloride well and use enough precipitate, not more, wash the gold powder well with hot water more time, the problem of Cu an Ag will probably be solved.is it true?*


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## Yggdrasil (May 23, 2022)

Gold.refinery said:


> Exactly, silver and copper were the biggest pollutants. We need 999 and 995 carats to sell products. Focusing on the subject of washing (copper and silver) is related to the unfavorable surface of the gold ingot after the final melting. To solve this problem, we were advised to wash the gold powder better. it's true?
> 
> I added a lot of water in one operation. According to *Frugal refiner*, I do not think we had silver in the gold powder.
> But in the last operation, I made the solution with more concentration and we had silver in end.
> ...


The copper would be out, but the silver is pretty close to not soluble in water.
So there is where and why some of our member use Ammonia.
Dilute Cold solution before filtering with a fine filter will remove this.
This should be done before precipitation of the gold.

Edit:
Did you figure out the plastic pipe function in your tank?
If not it is supposed to fill the dead space above your ball valve in your tank.
Such that all solution is stirred and agitated.


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## Gold.refinery (May 23, 2022)

silver1 said:


> Getting pure gold (shining)
> 
> 
> Hello, I would like to know what I must add/change to a standard AR process to get pure gold after melting it. Most of the gold buttons I get are not completly shining and seem to have a very thin layer of impurties. How can I correct that ? Thanks
> ...


Washing gold powder with a large volume is practical in this way !!!??


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## nickvc (May 23, 2022)

4metals said:


> These are images from another system. This is the smallest system I have ever worked with, I have photos of larger ones but these will suffice as an example. This is the tank where the gold is dropped and it is filtered. Basically they are all simply raised tanks which allow a filter to fit beneath. They usually have a slightly coned bottom to allow complete drainage, and some type of effective mixing. The photo on the top left shows the gold rinsed and sucked dry on removal from the tank, to it's right is the tank with the filter seen below. The next photo is just the system at another angle, and the last shows the mixer blade which is permanently fixed in the tank.
> 
> 
> View attachment 50255
> ...


4metals wouldn’t simply turning the tumbler on for a few turns. after precipitating the gold negate the need for a stirrer ?


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## 4metals (May 23, 2022)

nickvc said:


> 4metals wouldn’t simply turning the tumbler on for a few turns. after precipitating the gold negate the need for a stirrer ?


The tumbler is only used for digestion, the cementation tanks are used to precipitate. It is difficult to empty solids from the tumbler.


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## 4metals (May 23, 2022)

Gold.refinery said:


> You recommend, for example, for 15 kg of scrap that requires 15 liters of nitric, add 5 liters, after calming 5 liters, and finally the final 5 liters.
> Doesn't that cause more unresolved gold?


First do the math, better yet use the attached spreadsheet and go to the weight of the scrap, this example is 15kg or 482.25 ounces. The chart is in increments of 5 so choose the closest number. At 480 ounces you need 51.2 liters of Hydrochloric Acid and 12.8 liters of Nitric Acid. Add the gold first then all of the Hydrochloric Acid, then 1/3 of the Nitric Acid wait until you can see the red fume slow down then the second 1/3 of Nitric Acid again wait for the reaction to subside, and add the final 1/3 of the Nitric Acid. This is aqua regia at a 4:1 ratio and should effectively dissolve your scrap material.


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## 4metals (May 23, 2022)

Gold.refinery said:


> other way ; Can we just add hydrochloric acid and nitric acid for only 1/3 of the total scrap, then *filter the solution*, then add 1/3 of the total acid and so on.


That is a lot of extra work and you will be filtering and essentially doing the labor 3 times when the system is capable of doing the entire lot once.


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## 4metals (May 23, 2022)

Gold.refinery said:


> During the first 20 to 40 minutes of the acid reaction, we always have some *white fume *(with a low chlorine odor) in the chimneys after the scrubber.After the peak of the reaction, it ends.
> 
> This is not a good thing, from the neighbors' point of view.Of course, no one has objected so far.


What chemistry are you using in your scrubber? What is the airflow through your system, what is the volume of your scrubber? These three factors determine the ability of the scrubber to effectively scrub your fumes. 

Many years ago I knew a Russian chemist who worked in the NYC jewelry district. He was shocked to see a fume scrubber and when I asked him what he used for the fumes he said "refine at night. plenty wind!" 

We are in the middle of discussing your chemistry to get the refining right, I think going off into a discussion of your fume scrubbing will be a distraction. Why don't we wait until we get past the refining and are discussing waste treatment and fumes.


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## 4metals (May 23, 2022)

Gold.refinery said:


> Regarding the amount of precipitate, of course we see the reaction, but *knowing the amount *of material will help. Due to the toxicity of the precipitate and the health hazards, we do not like to see the reaction too often. Produces gas during settling.


I went back and looked at the photo you sent of your precipitation tank. The exhaust port looks to be about 2". That seems a bit inadequate to remove the fumes you will generate adding the chemicals and mixing. If you look at the system photos I attached earlier of a similar system their exhaust is about 4". That produces 4 times more exhaust. That is something you will have to address and deal with.



Gold.refinery said:


> Please explain more about the color change of the solution at this stage.


When the karat solution is dissolved it is usually green. The gold is actually yellow and it effects the color of the green. If you see it enough, you will be able to see the color shift from a bright vibrant green to a dull dark green when the gold has dropped. This is true with concentrated acids and karat gold.



Gold.refinery said:


> In the case of the stannous test, a few minutes after the end of the deposition reaction, we take a small amount of solution from the top of the tank to test, is this correct?
> 
> Your opinion is that if the gold deposit is done with experience and confidence, there is no need to leave the solution overnight, which is great for the production process. it's true?


It is best to get some solution from the lower depths of the tank not just the top but if it is mixed well yes it is correct.

And overnight should never be in the process for precipitated gold. Generally I like to see the digestion run at the end of the work day so the acid can slowly finish any dissolving overnight and be cool in the morning. The gold can be filtered, rinsed, and precipitated (and most likely melted) by lunchtime. The dissolving process is the longest process.


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## 4metals (May 23, 2022)

Gold.refinery said:


> In the case of washing powders, if we wash them with hot water, for example 5 times, will the *copper chloride* and the remaining base metal salts be washed ??
> Also, washing several times *causes gold to escape or not*?
> 
> In the case of drying, in the last operation, we left it on the filter for 30 minutes, it dried a little, but it was not desirable.
> I did not notice the drying of a large volume of gold sponge in the funnel.


Washing requires a strong stream of water to move the sponge about to rinse off the clinging acid that travels with the gold. That is the source of the. most contamination. Some refiners prefer to remove the gold from a filter and place it in a deep plastic tank so they can agitate and blast the gold with water, I always got by with a wand with a flat spray nozzle that I held close to the gold and moved it with the spray, avoiding splashing gold out of the funnel. Not saying I never shot some gold out of the funnel but with practice I got better. 

If the funnel has sufficient suction it should be able to dry the gold sufficiently. You have to keep the pump running to provide constant suction to dry the gold.


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## 4metals (May 23, 2022)

Gold.refinery said:


> I know that it is not problem to melt wet powder in a cold crucible, but the volume of our crucible is 5 kg and it is cold for the first time, then it is poured.


The size of your furnace is cause for concern. Refining has become a confusing industry. Once upon a time crucible capacities were rated in pounds of aluminum they could hold. Red brass was used for a time as well. Most clay graphite bilge crucibles are still rated by pounds of aluminum. But today a lot of induction furnaces are rated based on their capacity of pure (refined) gold. If your crucible is rated 5kg of 24k gold it is too small. 
When you melt your lots together to make a refining lot you will have the best success if you melt everything in the lot in one crucible and this way all of the shot will be the same karat and the same silver content. If you do smaller melts and mix the shot you have a few things to account for which can cause errors. First you have to add the gold contents of all the bars together to come up with an expected yield, much simpler with a single pin representing the entire lot. 
If you have 2 different lots and the silver content varies by as little as 1% that shot will not dissolve as well as the shot with lower silver. To get the best digestions, melting it all together is the best scenario. 
I know every self respecting refiner puffs out his chest and says “I melt with induction”. Well I’m old enough to have been around long before induction came to refining and for cost vs ounce capacity you cannot beat a gas furnace. Today you can get a gas furnace that holds a # 20 crucible for cheap and use it just to melt your bars into process lots. Your induction is fine to melt your final product or quickly melt smaller bars customers bring in, but having an old fashioned gas furnace tucked away in a corner will make your expected yield calculations easier and allow you to check on your individual bar assays as the final composite melt should produce the product of the individual bars. Plus all of the shot will be the same assay and prevent lots with higher Silver from causing lower yield's due to Silver Chloride encrustation.


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## orvi (May 24, 2022)

Gold.refinery said:


> There are two circles at the top of the reactor where we can see the reaction.
> 
> You recommend, for example, for 15 kg of scrap that requires 15 liters of nitric, add 5 liters, after calming 5 liters, and finally the final 5 liters.
> Doesn't that cause more unresolved gold?
> ...


It is wise to add the nitric acid stepwise. If the reaction gets too violent, it tend to boil in the vessel, and all the fizzing in the reactor create aerosols that carry the dissolved gold up the vent pipe. Eventually, they will stick to the walls of the tube and recondense back to the vessel. But if you have only 2" pipe, the flow velocity of gases/aerosols inside that tube will be 4 times more rapid than in 4" piping (area is pi x half diameter squared - so for 2" => 3,14" sq. ; for 4" => 12,5" sq. = vast difference) as 4 metals pointed out. That will cause some small ammount of gold to be carried with gasses eventually.
White fumes - i do not expect any salts to be produced in the process which are white, except silver chloride - that I doubt will go in gas out of scrubber. White fume could well be evaporated hydrochloric or nitric acid. If reaction is violent and boil, quite a bit of HCL and HNO3 could be boiled off.

It is very good to wash the precipitated gold with HCl, water and then ammonia. Different wash has different affinity to clean the gold from impurities. HCL will wash the CuCl very well (CuCl will form if you add too much precipitant = precipitant will firstly reduce gold, but if there is excess of it, it will reduce Cu(II) to Cu (I), which is much less soluble). HCL also removes some silver chloride, but it need to be washed repeatedly if you want to achieve some good cleaning efficiency for silver. Ammonia wash is much better in terms of reducing silver content, with ability to also wash the copper.
In larger apparatus, it could add quite a bit of work to wash numerous times. You also create waste which should be treated afterwards.
If you use excess of hydrazine (what you done apparently from the Cu precipitation), there will be no oxidizer left. So washing even numerous times with boiling HCL nor ammonia will not dissolve the gold. You can always test the washes with stannous to make sure. Stannous always tell you.

Also, washing the gold with HCl (hot) has benefit of coalescing the gold, so it could help to coalesce small particles that could pass the filter to the mother liquor.

There is also the possibility to clean the gold with proper oxidizing flux (eg nitrate/soda to remove copper when melting). But I do not know if this is suitable for operation this large. I think more experienced guys here will add to this.


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## Gold.refinery (May 24, 2022)

This video shows the different components of the filter.


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## Yggdrasil (May 24, 2022)

Gold.refinery said:


> This video shows the different components of the filter.


To my eyes the filter was too small or wrongly installed.
Is the liquid sucked to another tank under vacuum?


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## Gold.refinery (May 24, 2022)

Yggdrasil said:


> To my eyes the filter was too small or wrongly installed.
> Is the liquid sucked to another tank under vacuum?


Yes, it is transferred to another tank. What do you mean by small? The diameter of the inner ring is 60 cm.


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## silver1 (May 24, 2022)

Yggdrasil said:


> To my eyes the filter was too small or wrongly installed.
> Is the liquid sucked to another tank under vacuum?



Not part of this discussion, but based on the same concept that i built mine out of. Powered by a Shop Vac. I took the cheap route! Wonder what's the price on that thing?


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## 4metals (May 24, 2022)

Gold.refinery said:


> This video shows the different components of the filter.


As Yggdrasil said the filter paper appears to be too narrow to fill the diameter in at least one place. If the paper does not fit under the ring that you place on top to hold the paper down solution and values will go under the paper and cause poor filtration. 

Typically filter paper is available in the diameter to match the diameter of the fabric filter which makes placing it in the filter much easier. You can make a cardboard template by tracing the fabric filter and using scissors cut the paper before putting it in. Makes for a better seal as it will lay flat and it just makes life easier. 

This type of filter is made to work off a double diaphragm pump. Double diaphragm pumps can run dry with no damage to the pump and will create a vacuum to pull the liquids through the filter. Then the pump will transfer the liquids to wherever the plumbing connects. 

You had mentioned that your gold sponge did not dry sufficiently on the filter. This makes me question wether you have a double diaphragm pump which can pull a decent vacuum. What type of pump do you have? Maybe a photo?


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## Gold.refinery (May 24, 2022)

4metals said:


> What type of pump do you have? Maybe a photo?


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## 4metals (May 24, 2022)

That appears to be a double diaphragm pump. It feeds from the top, where the intake can be switched by a valve? And the bottom is the discharge.

Also, after looking closer at your video, I see the bottom of the filter is flat. That makes it all the more important you open it up after every use and rinse the liquids on the bottom clear.


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## Yggdrasil (May 24, 2022)

Gold.refinery said:


> Yes, it is transferred to another tank. What do you mean by small? The diameter of the inner ring is 60 cm.


I meant the filter paper do not cover the whole area.


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## 4metals (May 24, 2022)

I think Gold Refinery realizes by now that filtration is critical to the final purity of his gold. Showing us detailed photo's has been helpful because it is easy to spot small inconsistencies, as Yggdrasil just pointed out.


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## 4metals (May 24, 2022)

I think, on the subject of filtration, your filters are a weak link in your system. The pump used on the filter is strong enough to do the job properly but I think the design of the filter is a problem. The actual filter media is only propped up from the bottom by a short distance. I think this is the issue. In other systems the area beneath the filter is large enough to form a vacuum reservoir. The vacuum is powerful enough to warrant a center support to prevent the flat filter plate that holds the paper from bowing down. It is entirely possible that your plate bows down and actually inhibits suction. 

These are photos of what is under the deck on an Italian system, note how large the under plate area is. 


The paper is held in place with a rubber gasket which sits between the plate and a lip to securely hold down the paper and screen to the perforated plate.


This gasket has to be pushed in by hand to make the seal. 


The pump is permanently mounted to the moveable base so the filter can move about the shop. 




And Ralph, don't even ask what these cost!!!!!!


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## Yggdrasil (May 24, 2022)

4metals said:


> I think Gold Refinery realizes by now that filtration is critical to the final purity of his gold. Showing us detailed photo's has been helpful because it is easy to spot small inconsistencies, as Yggdrasil just pointed out.


It may be an accident while showing us his system.
That’s why I asked.


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## 4metals (May 24, 2022)

This is what the de-watered gold sponge in the Italian filter looks like. Enough moisture has been sucked out for the cake of gold sponge to crack because there isn't enough moisture to keep it together. This gold is ready for transfer to a melt furnace without further drying.


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## 4metals (May 24, 2022)

Yggdrasil said:


> It may be an accident while showing us his system.


I think in the long run it will benefit him as he will know what he needs to do to get the equipment to perform at the level he needs. 

But the manufacturer should be embarrassed!


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## Yggdrasil (May 24, 2022)

4metals said:


> This is what the de-watered gold sponge in the Italian filter looks like. Enough moisture has been sucked out for the cake of gold sponge to crack because there isn't enough moisture to keep it together. This gold is ready for transfer to a melt furnace without further drying.
> View attachment 50301


Now I became curious, how do you lift out something like that without dropping anything

That is a challenge I’d love to have one day

Edited for readability


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## 4metals (May 24, 2022)

Yggdrasil said:


> Now I became curious, how do you lift out something like that without dropping anything


That is actually a challenge, usually the gold is dry enough to lift out the larger chunks and then, with a small dustpan, brush the loose gold into the pan. When most of the loose gold is out, the gasket is removed, and the paper is carefully lifted from the edge so anything loose falls to the center. They continue around the diameter lifting until the sheet is out from under the lip and the remaining gold is towards the center, then the entire sheet is lifted out. 
Ripping the paper is the biggest problem but in a short time with a few practice loads it becomes routine.


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## Gold.refinery (May 24, 2022)

*Stannous chloride Test:*
I made a stannous chloride solution with the formula 4metal. 
We have now tested some of the yellow solution that remained in the cylinder filter. See the details in the video. 
Please guide me with more details. 
Where should I drain the brown solution? Where should I sample the gold tank? 
What is it like to test dirty solutions after depositing gold in the next tanks?


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## Gold.refinery (May 24, 2022)

4metals said:


> usually the gold is dry enough to lift out the larger chunks and then, with a small dustpan, brush the loose gold into the pan.


We could not dry the gold sponge in the last operation as much as the photo you sent with diaphragm pump.
Then, for better drying, we poured it in a steel container (????) and dried it with heat. 
A lot of time wasted. We got bored.
I think some impurities (Fe) also entered the pure gold powder, which at the end of melting, made the surface of the ingot difficult.

*What to do for quick drying without deducting gold and impurities?*


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## Gold.refinery (May 24, 2022)

Yggdrasil said:


> I meant the filter paper do not cover the whole area.


Paper filter suppliers are not larger than 58 cm. They also do not know the size of the mesh. !!!! 
*We are looking for a roll paper filter with a 2.5 micron mesh.

Another solution is to make the filter gasket 2cm wider.*

Question: 
Depending on the type of our pump that was sent in the photo, is it necessary to replace the grid under the filter, which has large holes, with a 5 mm hole grid? (according to Italian systems)


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## Gold.refinery (May 24, 2022)

I have many questions about different topics, but I will not mention them yet, to focus on the topics. Please, after completing this route, (4metal) , 
I will ask some *questions*, 
also you *confirm* what I learned from members.


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## 4metals (May 24, 2022)

Gold.refinery said:


> Where should I drain the brown solution? Where should I sample the gold tank?


The solution in the canister filter is definitely holding gold, as confirmed by the stannous chloride. And you were of the opinion you rinsed it thoroughly. That is why those filters have no place in the line with gold laden aqua regia.

The brown solution has gold in it and is difficult to filter. For this reason I never test in solution as you did in the video. If you were to pour out the liquid and use a piece of filter paper or paper towel to hold the sample you test. Simply dip the end of the paper into the liquid and let a small amount be absorbed, or use a glass rod and dip it in the liquid and allow those drops to drip on the paper. Then you add your drop of stannous chloride to the drips of sample on the paper. It will indicate accurately and you have used very little liquid. The papers are collected in a container where they can be accumulated and later burned and sent out for refining. (The manufacturers of these tumbler plants often say they can process sweeps for gold. Filtration is difficult and you never get all of the values.)
The remaining liquid (only if you have not added stannous chloride) can be put in the tank where you will be doing your next gold drop. 

My suggestion, take that filter out of the line once you get the filtration process in your big filter ironed out. 

You can stir the liquid in the gold tank and sample the liquid the same way, by wetting a glass rod and adding a few drops to filter paper.


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## 4metals (May 24, 2022)

Gold.refinery said:


> What to do for quick drying without deducting gold and impurities?


If you have to dry in a metal container, use stainless steel trays. 

If you send a few photos of the inside of the filter you showed us in the video so we can see just how high above the base the plate sits. Perhaps we can figure a way to get you some space under the filter which may help. That filter, working properly, will save you time.


Gold.refinery said:


> A lot of time wasted. We got bored.


and prevent boredom!!!!


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## 4metals (May 24, 2022)

Gold.refinery said:


> Question:
> Depending on the type of our pump that was sent in the photo, is it necessary to replace the grid under the filter, which has large holes, with a 5 mm hole grid? (according to Italian systems)


It's not the size of the holes because the fabric is supporting the paper. The issue, I believe, is the fact that you cannot generate a sufficient vacuum reservoir under the plate because the grid is so close to the bottom. If you notice the Italians have a much greater space under the grid. Their pump is as good as yours so that is not the issue. 

You also need to have the entire edge of the filter paper under the gasket. If solution can sneak around the edges the vacuum will take the easiest path too and a strong vacuum will never develop. 

For now, if 58 cm papers are all that are available, have a wider gasket made and cut 58 cm circles to put into the filter. The guys can do it while waiting for the gold to dry!


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## Gold.refinery (May 24, 2022)

4metals said:


> If you send a few photos of the inside of the filter you showed us in the video so we can see just how high above the base the plate sits


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## 4metals (May 24, 2022)

Looks like the grid sits at most 4mm off the bottom. 

The ring that holds the grid off the bottom that is fixed to the bottom is all that is lifting the grid? Is it the same as the piece you put on top of the paper to seal the papers? 

If it is, and you have a few of them can you try to put 2 more down under the grid to raise it? Then you can cut some short lengths of PVC pipe the height of the stacked spacers. The pipe will support the grid which I fear will bow downward. If you place a few of the pieces of pipe around the center we may be able to prop up the grid enough and create an airspace below.


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## 4metals (May 24, 2022)

I just looked more closely at the video. That grid sits completely flat on the bottom inside the ring. That is the problem. We need to raise the grid at least an inch, preferably 2. (5cm) off the bottom. This may be something the manufacturer of this equipment can do for you. 

If the manufacturer can add a few rings to the filter body so the grid is 5cm higher and add the equivalent spacers to the grid so it sits above the bottom it will be better. You will still need the short pipe pieces (with scalloped ends so they drain) to place under the grid because you can see when it is lifted it bends.


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## silver1 (May 24, 2022)

4metals said:


> I think, on the subject of filtration, your filters are a weak link in your system. The pump used on the filter is strong enough to do the job properly but I think the design of the filter is a problem. The actual filter media is only propped up from the bottom by a short distance. I think this is the issue. In other systems the area beneath the filter is large enough to form a vacuum reservoir. The vacuum is powerful enough to warrant a center support to prevent the flat filter plate that holds the paper from bowing down. It is entirely possible that your plate bows down and actually inhibits suction.
> 
> These are photos of what is under the deck on an Italian system, note how large the under plate area is.
> View attachment 50296
> ...




 Oh i know better!

You're right as i think about, not enough space under the plate. I ran into the same problem with my first design concept. 

An easy fix could also be made with a 3d printer cheap and effectively.


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## AMS-Pro (May 24, 2022)

I believe I'll chime in at this point. 

First, I'd like to say thank you to 4metals for inviting us all together on this one, the private message was definitely a bit bare on information.
I would say the filter picture in your second post of this thread definitely looked troublesome. I thought maybe it was just the angle of the picture, but it appears not to be.

Nitpicking out of the way first:

I do have a problem with the valves shown (orange handle), I feel that the internal design of the flap (I'm assuming its a butterfly style) may catch sediment, but this would only be a very small amount. As far as valves go, I'm a fan of knife gate with a cleanout access.

Some of the elbows, and angle of piping seems either sharp or severe in some areas, and could affect flow rates, or where hidden deposits of sediment could build.

Both of these nitpicks could cause a loss, but it would relatively minimal at the scale we're discussing.

Onto the Filter:

A client of mine had a similar setup to what was pictured here, there were several problems that it posed:

1: Once the filter material started to get packed, usually from the center out, the edges would start seeing a higher flow rate and would slightly lift/curl the edges. and cause the seal to get pulled or loosen. 

2: We had also come to a determination with the holes in bottom of the housing were a bit large and the filter material was allowed just enough space to settle into them slightly, like tiny little puddles potholes. With enough of those little indents (potholes/puddles) added together, it had pulled the filter taught/inward on the edges, which in turn would aid in the seal loosening. 

3: Cleanout of the dry/cake material was a pain, it seemed you could never get it all. This was mainly seen when the seal and filter material were pulled, it seems the sediment would collect/ get packed between the filter material and the seal, and between the seal and the housing. Although this is not quite a loss as it is able to be collected, recovering all the sediment that had found its way into the seam (where the edge of the filter material/seal was pressed into) was extremely tedious to get recover, and would cause a poor seal on the next run if care was not taken to recover every last bit. 

This problem seemed to build with every run, and the quality of the seal worsened slightly ever time. This resulted in the filter material becoming dislodged more often as time went on, number of runs increased. 

The solution we came to for my clients setup was to modify the internal area of the filtration chamber, and it was converted to a multi bag setup. We had designed a drop in skeletal system in CAD to fit the existing chamber perfectly. The skeletal system had 9 vertical mesh cylinder chambers that the bags could drop into, the top plate of the skeleton system was welded into the existing chamber to eliminate any chance of sediment buildup on the edge. The inspiration for the idea came from a filtration system designed by a company named *PRMFiltration*, but like the OP here, my client already had a chamber that we could work with, so we just designed an insert.. 

Below I have inserted some pictures from the *PRMFiltration *website that gives you an idea of what I am referencing, you can look on their website for setups that more closely relate to yours. 

Since we have converted my clients setup over this to this, cleanups have become much, much easier, and the previous issues we had are no longer present.


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## Gold.refinery (May 24, 2022)

orvi said:


> I do not understand why you want to test tin, but I assume you wanted to test gold with tin (II) chloride. Correct me if I am wrong.
> 
> It is wise to take one afternoon and *get familiar with stannous chloride* test.* It´s quick, cheap, straightforward and work to quite a dilution* (good test can catch 0,1g/L gold, if trained eye is watching).
> 
> ...


I made the standard gold solution. Dissolve 0.1 grams of pure gold in AR , Then add about 100 ml liters of water. 
Then I tested with different concentrations with stannous chloride. 
Different colors were created. 

But the question is whether the solution we want to test during the refining operation is opaque green, and combines with the colors shown Below. 
How to recognize?


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## 4metals (May 24, 2022)

When the acid is a combination of the gold and copper and zinc in the alloy you are refining it will be a green solution. If the acid has a few grams of gold per liter it will instantly become a dark black liquid and easy to recognize. 
I think you will find it easier to identify the different concentrations if tested on paper.


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## orvi (May 25, 2022)

Gold.refinery said:


> I made the standard gold solution. Dissolve 0.1 grams of pure gold in AR , Then add about 100 ml liters of water.
> Then I tested with different concentrations with stannous chloride.
> Different colors were created.
> 
> ...


I agree with 4metals, drop testing on filter paper would be more accurate to distinguish. You are looking for violet-dark-black colour. You have an advantae, that your solutions are highly concentrated, and as you have seen, 1g/L gold produce completely black test - so you can be testing even the greenest liquid, that flip to completely opaque black colour you cannot miss.

This show your stannous work, but I am curious about all of the colours from 0,25g down. Maybe it is just a photo, but they seem to be still orange (impurity ?) and precipitate or opalescence is rather brownish than violet/black.


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## silver1 (May 25, 2022)




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## 4metals (May 25, 2022)

I've re-read what amounts to 6 full pages of this thread and realize that gold Refinery has equipment issues which he appears to be working through, and then there are chemistry issues which to this point have been untouched beyond dissolving of the gold scrap. So let's try to keep this organized by working thru step by step. We will start with chemistry of refining gold and move on later to fume scrubbing, cementation, waste treatment and any other pertinent topics in an orderly (hopefully) fashion.

It is time to discuss chemistry options to button up the actual refining process. To make things easier it will help to know the OP's access to chemicals. Is sulfamic acid available to you? How about sodium metabisulfite? 

For the next day or so we will be assuming the well filtered solution is sitting in the precipitation tank awaiting processing. Please Gold Refinery detail what steps come next in your current process. Don't be shy with photos, we have seen how actual photos so far in this thread have revealed much in helping us help you.


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## 4metals (May 25, 2022)

silver1 said:


> Not part of this discussion, but based on the same concept that i built mine out of. Powered by a Shop Vac. I took the cheap route! Wonder what's the price on that thing?


Ralph,

I love listening to your video's, I also enjoy listening to your (slightly) southern accent. A bit different than my New York accent! 

I think your filter might offer Gold Refinery a solution here. The pump he has to draw vacuum in his filter could do the same here and transfer the solution downstream just as it does with his current filter. My concerns are the seal between the inner bucket and the outer bucket but possibly a strip of rubber cut from a tire tube stretched around the inner bucket may solve that. Also it may be necessary to cut a third bucket to make a ring to go inside the inner bucket and seal the paper down. 

But all things considered, considering he has the pump, the price is right and the removable bucket is easily emptied because it isn't too heavy to lift out.


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## Gold.refinery (May 25, 2022)

4metals said:


> It is time to discuss chemistry options to button up the actual refining process. To make things easier it will help to know the OP's access to chemicals. Is sulfamic acid available to you? How about sodium metabisulfite?


I did not follow sulfamic acid until now in the market, but we have SMB available in the workshop. 
We also have hydrazine 55%.


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## 4metals (May 25, 2022)

Most of the suppliers of tumbler plant refining systems recommend urea to burn off excess Nitric Acid and sodium metabisulfite to drop the gold. Personally I would be staying away from the hydrazine. 
The metabisulfite is quick and efficient at dropping gold once the nitric has been consumed. The urea is not my favorite because it will cause waste treatment issues down the line as it will decompose into ammonia which will redissolve copper into your waste stream. That is why you should investigate sulfamic acid. 
Discussing the various options of dropping the gold is where the various methods used by members will help present Gold Refinery with all of the potential options. So I invite other opinions for sure.


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## Gold.refinery (May 25, 2022)

Yes right, I did the final Final purification of the solution, after adding the caustic soda, the smell of ammonia filled completely in the workshop space. So I will definitely follow sulfamic acid. I just heard that it is expensive. I also do not know the ratio of its use. 

As for the precipitate, from there we are in a busy commercial area, the manufacturer of machine suggested hydrazine. (I hate it). 
We predicted that *SO2* gas could cause irritation to neighbors's eyes and noses. 
Of course, after discussing the capacity of *scrubbers* and their chemistry, this issue may become clear.


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## 4metals (May 25, 2022)

Gold.refinery said:


> the manufacturer of machine suggested hydrazine. (I hate it).


Is this the same guy who said use 58cm paper to fill a 60cm diameter plate? Or mixed you up a liter of Stannous chloride so you have enough for years of refining? 

I have used hydrazine extensively to reduce platinum group salts to metal but not ever to drop gold. Hydrazine will drop gold with free nitric so I do not know why you were instructed to add so much urea. If there is Platinum or Palladium in the jewelry you melt and refine, I do not know if the long standing (overnight) exposure to hydrazine will reduce them along with the gold. As I said I never used hydrazine to drop gold, possibly Lou will know the answer to this. Here in the US it is heavily regulated so options are often considered to limit its use.


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## Gold.refinery (May 25, 2022)

Unfortunately, this is the same person who made the 2 liter tin chloride solution !!!! 

Did I get what you mean? Do you believe that if hydrazine is used to precipitate gold, there is no need to kill nitric with urea ???? 

The platinum and palladium in our scrap are very very small, so we are not going to take the platinum group right now, 
assuming, is not hydrazine suitable? 
Also, what is your opinion about so2 gas from smb?


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## 4metals (May 25, 2022)

Gold.refinery said:


> Also, what is your opinion about so2 gas from smb?


The Sulfur Dioxide fume is much more water soluble than a NOx fume and European standard fume scrubbing usually can accommodate Sulfur Dioxide, it's NOx where there is a retention time issue, which we can discuss later. 
Another option for dropping the gold is Sulfur Dioxide gas cylinders. It can drive off the excess Nitric by dropping gold and allowing the nitric to burn off by re-dissolving gold until the gold drops and stays dropped because the nitric is gone. And gaseous Sulfur Dioxide drops gold very clean. 

A last option which has very low odor is Vitamin C or Ascorbic Acid. I know some smaller scale refiners using it and maybe someone with first hand experience with it will chime in here.


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## orvi (May 25, 2022)

Gold.refinery said:


> Yes right, I did the final Final purification of the solution, after adding the caustic soda, the smell of ammonia filled completely in the workshop space. So I will definitely follow sulfamic acid. I just heard that it is expensive. I also do not know the ratio of its use.
> 
> As for the precipitate, from there we are in a busy commercial area, the manufacturer of machine suggested hydrazine. (I hate it).
> We predicted that *SO2* gas could cause irritation to neighbors's eyes and noses.
> Of course, after discussing the capacity of *scrubbers* and their chemistry, this issue may become clear.


I do not know from what perspective you judge the "expensiveness" of chemicals, but here I purchase it for about 5euro/kg. If you do not overshoot with nitric that much, you won´t need more than one or two cups to neutralize the solution. Not even half a kilo. For me, if I would refine 2,9 kilograms of gold, some 2 euros extra money will be practically nothing  And I am purchasing kilo packages, not in bulk. It will get even cheaper in bulk. 
Sulfamic acid is industrial chemical, often used for de-scaling.

I do not know to choose what is better - to slightly smell severly poisonous and carcinogenic hydrazine, or strong smelling probably less toxic SO2 (just in my view, poisonong with SO2 is much more difficult because unbearable smell in very low concentrations).
If you do not overadd the metabisulfite, not that much SO2 will escape the vessel. You have very concentrated gold solution, so majority of SO2 will be consumed to reduce gold. So sulfur will in turn oxidize to S(VI) - forming sulfate ions, which do not smell and are practically harmless.

As it ws said, if you ever stumble across PGMs in your solution, hydrazine will reduce them to metals, too. Maybe you do not have the PGMs in your feed now, but if they emerge in the future, you won´t have the means to get rid of them from your gold.

Other possibilities for reducing gold are all quite impractical in my eyes. Ferrous sulfate is overkill - too much waste weight, lots of it for reducing this large batches, and subsequently enlarged waste stream.
Ascorbic acid is expensive, oxalic acid is quite impractical with need for prolonged boiling... 
SMB is winner for me.


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## Gold.refinery (May 25, 2022)

Our scrubs can purify NOx gases completely, so, do you think they will purify so2 gases as well?

If we use so2 gas, there is no need for the free nitric killing step, right? 

If we use so2 gas, will all the solutions have an annoying smell until they reach the end and treat the wastewater? Also smb?


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## 4metals (May 25, 2022)

Gold.refinery said:


> The platinum and palladium in our scrap are very very small, so we are not going to take the platinum group right now,


Stannous chloride will also indicate Platinum and Palladium in your acid after the gold has dropped. The intensity of the positive gold test on your solution will mask the PGM's so you will not see it until the gold is out. 

If it is even a few grams in solution the stannous will indicate it. for this reason you need to learn what the color changes are for the Platinum group metals. This is part of the learned art of refining that experience brings.


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## 4metals (May 25, 2022)

Gold.refinery said:


> If we use so2 gas, there is no need for the free nitric killing step, right?
> 
> If we use so2 gas, will all the solutions have an annoying smell until they reach the end and treat the wastewater? Also smb?


Sulfur Dioxide will eliminate the need for sulfamic acid or urea, but is likely more costly than sulfamic. It works by burning off the excess nitric because it drops gold, which re-dissolves to be dropped again based on how much free nitric remains. By killing off with sulfamic, you will use substantially less Sulfur Dioxide gas. Either way you have to kill off excess nitric acid unless you choose hydrazine which is not my first choice. And with hydrazine, if there are PGM's in solution they will be in with your gold as Orvi confirmed. Then the only way to get them out is to re-refine the gold. 

The annoying smell is probably from the urea in a caustic solution becoming ammonia. Not an issue with Sulfur Dioxide or metabisulfite. In either event, you should consider a general exhaust to get those fumes out of your shop. Waste treatment over an unvented tank isn't conducive to the best of working conditions.


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## orvi (May 25, 2022)

4metals said:


> The Sulfur Dioxide fume is much more water soluble than a NOx fume and European standard fume scrubbing usually can accommodate Sulfur Dioxide, it's NOx where there is a retention time issue, which we can discuss later.
> Another option for dropping the gold is Sulfur Dioxide gas cylinders. It can drive off the excess Nitric by dropping gold and allowing the nitric to burn off by re-dissolving gold until the gold drops and stays dropped because the nitric is gone. And gaseous Sulfur Dioxide drops gold very clean.
> 
> A last option which has very low odor is Vitamin C or Ascorbic Acid. I know some smaller scale refiners using it and maybe someone with first hand experience with it will chime in here.


Well explained. Nox is much difficult to scrubb or destroy. SO2 is acidic, so very simple "basic" absorber with NaOH is usually enough to catch vast majority to acceptable levels.

I just add that with good fitting and fritted glass on the end of the SO2 delivery tube, you can very easily adsorb majority of the gas without significant escape to the air. 

Vitamin C is fine, produce good precipitate I think. But I only used it for gram scale drop. Not for production scale.


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## Gold.refinery (May 25, 2022)

orvi said:


> I just add that with good fitting and fritted glass on the end of the SO2 delivery tube, you can very easily adsorb majority of the gas without significant escape to the air.


Would you please explaine more , I didn’t understand.


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## 4metals (May 25, 2022)

Sulfur Dioxide is typically delivered through a tube which reaches down low into the tank and forces the gas to contact more solution as it rises. Much like an airstone in an aquarium which makes more surface area by making smaller bubbles, a glass frit is the all glass "airstone" which allows more bubble surface area to utilize the Sulfur Dioxide more efficiency to react more completely before it passes out of the solution.


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## Gold.refinery (May 25, 2022)

I know so2 creates the best gold Sediment. 
Is the smell of sulfur created by so2 gas Sedimentation more or by SMB? 

Now, We have food grade SMB available. 
If we want to use SMB to deposit gold in the next operation, what points should we follow? 

For example, what is the ratio of adding smb to gold? (Helps for less gas and less pollution of gold dust). 

Do we have to dissolve it with water and add it or can it be added solid? 

In terms of time, how long does smb deposition take (compared to hydrazine)?


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## Shark (May 25, 2022)

How well would sodium nitrite work at this scale?


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## Geo (May 25, 2022)

A very good alternative for removing overages of nitric acid from solution before dropping the gold is sulfamic acid. Sulfamic acid is sold as grout cleaner for cleaning the cement that holds the stone tiles in kitchens and bath rooms. The formula is (H3NSO3). I suggest you incorporate this chemical to your process. The use of this chemical is fairly simple. Heat the solution to 93°-94°C. It is the best to use this chemical dry, if possible. Or, it can be added in a concentrated solution. The first amount added should be relative to amount of solution you are adding to, and, available room for gas expansion. I add 1 gram per 1,000ml's. It will produce a vigorous reaction if there is free nitric acid available in solution. After the initial addition, the next addition will be more subdued. The subsequent additions will be even more subdued. Make additions until there is no more reaction. This does not mean that the solution is nitric acid free. The solution should stay at heat and checked every thirty minutes. If the solution is generating N2O, which is a clear gas, do not add more. If the solution is producing NO2, which is a red gas that is noxious and corrosive and you need to add more sulfamic acid. Begin the additions the same as before. Small amounts until the initial gaseous outburst and then you can add bigger amounts at a time. While on heat, after thirty minutes, if the solution is not creating tiny reaction bubbles, the reaction is complete. The reaction generates a small amount of sulfuric acid in solution. This may cause some sulfate salts to form in solution, so it is best to filter after this stage.


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## orvi (May 26, 2022)

I would just add that reaction of sulfamic acid with nitric acid starts around 75-80 °C, but it is wise to heat it past this temperature to speed up the process. Timed additions are necessary to see if the nitric/NOCl/nitrous acid are still present.

Easily said for Gold.refinery:

Generally, you add sulfamic acid similarly as urea - heat the solution to at least 80 °C, add sulfamic SLOWLY until it stop fizzing (not to foam over), then you wait at least 15 minutes - or better 30 minutes and add little ammount and observe if there is some fizzing. If it still reacts, add more and repeat the waiting step.

Be aware of the fact, that fizzing liquid in open beakers or reactors create aerosols, which carry your gold solution away. Best is to prevent this by using larger container, so liquid is well below the top of the vessel and popping bubbles cannot shoot the liquid out of the vessel 


Gold.refinery said:


> I know so2 creates the best gold Sediment.
> Is the smell of sulfur created by so2 gas Sedimentation more or by SMB?
> 
> Now, We have food grade SMB available.
> ...



Both reagents (SO2 and SMB) smell like SO2, because SO2 is formed from SMB when reacting with acid in solution. SO2 gas coulld be very well regulated and bubbled from the cylinder - very very convenient. You can set up, open the valve and happily observe how the solution is losing the yellow colour while gold settle to the bottom  And you will see with stannous how much gold you have in solution - so you adjust the next addition of gas. 

Also, there is another advantage of using SO2 gas over metabisulfite. With sodium metabisulfite, you consume one equivalent of HCl to generate active SO2 gas - which actually reduce your gold.
SO2 is already an acidic gas - so it does not deplete your acid. 

If the acid is depleated (concentration/strength goes down), impurities like silver chloride or copper (I) chloride become less soluble and drop together with gold.

That is why SO2 gas produce cleanest precipitate of gold. As established refinery, I would suggest to invest and purchase SO2 gas cylinder. It can be regulated very well, do not add contaminants, easily added to the solution via tube... 

We need some photos or details about your scrubber - if it can scrubb the NOx gasses, I think it will scrubb also SO2 gas. Or there can be added simple NaOH bubbler at the end of your system - which catch like 90% of SO2 in first pass. And that would be enough to reduce the smell.


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## nickvc (May 26, 2022)

4metals said:


> The Sulfur Dioxide fume is much more water soluble than a NOx fume and European standard fume scrubbing usually can accommodate Sulfur Dioxide, it's NOx where there is a retention time issue, which we can discuss later.
> Another option for dropping the gold is Sulfur Dioxide gas cylinders. It can drive off the excess Nitric by dropping gold and allowing the nitric to burn off by re-dissolving gold until the gold drops and stays dropped because the nitric is gone. And gaseous Sulfur Dioxide drops gold very clean.
> 
> A last option which has very low odor is Vitamin C or Ascorbic Acid. I know some smaller scale refiners using it and maybe someone with first hand experience with it will chime in here.



4metals I have used ascorbic over many years but have tended to use ferrous for the majority of the drop and finished with ascorbic to limit the amount of iron in the precipitate , again I fed ferrous directly into the pregnant solution so long as it was bright green and I did drops of 2-3 kilos regularly with little problem.


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## Gold.refinery (May 26, 2022)

*Important:*

Brainstorming is great, different suggestions will also be helpful. 
But we need to know that we want to implement these solutions for a *large-scale* refinery. 
We should not reinvent the wheel. 

Here different members offer their suggestions, but a refiner will definitely come up with a solution that they can repeat *every day*. 
With maximum efficiency and minimum pollution. 
Refining is a very *dirty job*, and its *fees are very low*. (But in large volumes). 
So our suggestions must be Accurate.

I stopped refining operations to summarize the results of the topics in the forum.


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## Gold.refinery (May 26, 2022)

I asked several times about the ratio of chemicals used in the reactions, but only suggestions were made on how to calculate the acids, for the other of the chemicals did not provide ratios: precipitator (SMB,So2,Hyd,FeSo4,Ascorbic) , diluent water , Urea, Sulfamic Acid, NaOH,…

A table in Excel can specify the entire ratio of values.


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## Yggdrasil (May 26, 2022)

Gold.refinery said:


> I asked several times about the ratio of chemicals used in the reactions, but only suggestions were made on how to calculate the acids, for the other of the chemicals did not provide ratios: precipitator (SMB,So2,Hyd,FeSo4,Ascorbic) , diluent water , Urea, Sulfamic Acid, NaOH,…
> 
> A table in Excel can specify the entire ratio of values.


One of the issues here is that for 
most if us, no batch is identical. 
So we depend upon a general idea, 
but have to differentiate each reaction on what we observe and can 
measure (Stannous).

For SMB it is simple,
if you have a Nitric free, 
relative acidic and clean Gold solution, you need 1:1 by weight.

But that is paper values that are not much worth in the real world of precipitating Gold from various 
solutions, 
each one needs individual attention, 
it’s own TLC to perform the best. 

We are not avoiding the questions, 
but they do not have an answer 
set in stone. 
Stochiometric calculations can be done easily enough, but it will not take you all the way home.


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## Gold.refinery (May 26, 2022)

I know everyone has their own solution. 
And this is achieved after various experiences. 

Since an inexperienced operator works first with skepticism, knowing the approximate values will be helpful. 
By approaching the values, it can detect more confidently. 
Of course, I know that after a while, these numbers will only remain on paper. 

Guys, please provide stoichiometric calculations of all chemical.


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## Yggdrasil (May 26, 2022)

I’m not sure what your main language are, but you did not understand what I tried to tell you.
I’ll try this way:
No two batches are identical. 
Most approach this by adding what they expect is needed, and adjust as necessary.
Almost always more are needed.
There are adaptations of course, 
like with the Nitric as you have picked up already. If time is of little concern the AR process or any other Nitric process can be completed lower than stochiometric.

But you surely have an chemist at hand to do your calculations?

Are you able to read or balance chemical reactions?


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## Yggdrasil (May 26, 2022)

Gold.refinery said:


> I know everyone has their own solution.
> And this is achieved after various experiences.
> 
> Since an inexperienced operator works first with skepticism, knowing the approximate values will be helpful.
> ...


It’s hard to give any answer to this:
The processes you have outlined so far is AR for dissolving,
Hydrazine for dropping
(should be swapped to SMB)

For AR the most chemically effective method is with all HCl and half or so Nitric to start with, then batch wise addition until completed, with heating and a reflux condenser.
Since this is outside your specs, you can do the same without heating and overshoot the Nitric.
For completing the reaction in short time, you will have to overshoot quite a bit and as such no parts can be calculated other than the initial estimation.
For Sulfamic Acid the same goes, since it is completely dependent on how much you overshot the Nitric.

If you go through these two steps, with proper filtering so you end up with a completely clear Nitric free and highly acidic solution, the SMB to Gold Ratio is 1 to 1 in weight. 1 gram SMB gives 1 gram Gold.
Most will overshoot the SMB quite a bit to make sure all the gold drop.

So you see it is not possible to answer your question with X parts this and Y parts that will give Z parts this.
The rest of the alphabet mingles in.


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## 4metals (May 26, 2022)

Yggdrasil said:


> No two batches are identical.
> Most approach this by adding what they expect is needed, and adjust as necessary.
> Almost always more are needed.
> There are adaptations of course,
> like with the Nitric as you have picked up already. If time is of little concern the AR process or any other Nitric process can be completed lower than stochiometric.


Very true and cannot be overstated.

How would you calculate an exact amount of Sulfur Dioxide gas to add? Can you tell us the depth of solution you will gas into, or the bubble size the sintered glass frit provides? Or the temperature of the solution. These factors effect the quantity of gas used, as does the gold concentration. It is not as easy as looking at a balanced equation and saying add X and you’re done.

Gold Refiner, since your last flurry of insistence for specifics I have heard by PM from members frustrated with your attitude. And you have again started PMing me to ask questions off forum.

*Let me make this clear*, I will no longer be answering questions on this topic by PM and it is my hope neither will others. All questions should be on the open forum. That is what forums are about, helping each other. And you seem to want a one way street.

If your inquiries when you purchased your refining system matched the degree of your questioning here maybe you wouldn’t be having these issues. You are being given good advice here and it will result in solving your issues to the point where they will meet your goals. Something the manufacturer either didn’t give you, or you were unwilling to pay for. 

As you may sense, I’m a bit irritated this morning. As another member often reminds us, it’s time for more coffee.


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## Shark (May 26, 2022)

Thank you 4metals for trying to keep this on the forum. This discussion has been a real glimpse into the professional side of refining and a real eye opener for us small refiners.


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## 4metals (May 26, 2022)

To get back on track here we should ask if it is feasible for Gold Refinery to get bottles of Sulfur Dioxide gas. 
I have used sulfamic acid extensively but as Geo mentioned it has always been in heated Phaudler reactors. I think for this application perhaps a hybrid application is in order. 
The precipitating tank Gold Refinery is using is not heated and that will be an issue. I would be trying gaseous Sulfur Dioxide and allowing the reaction to heat up as the Sulfur Dioxide reacts. When it gets warm and is still blowing red fumes, powdered sulfamic acid can be added to assist in the consumption of the free nitric. This scenario is desirable because the rate of NOx coming off the reaction is directly proportional to the Sulfur Dioxide addition rate. So simply throttling back on the feed will give Gold Refinery control if there are scrubbing issues. 
Even if sulfamic acid is not added the Sulfur Dioxide will drop the gold completely and eliminate the free nitric. 
Gold Refinery has mentioned using a flocculant. I would like to hear more about what is used and the logic behind it.


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## Gold.refinery (May 26, 2022)

Sorry about that, I should have shared these topics *before* buying machines from the manufacturer. Too late unfortunately .

Our Tumbler can not heated , The gold precipitation tank also can not be heated. 
So we do not have an easy way to use sulfamic acid. To run the *hybrid way* mentioned by 4metal, operator has a difficult Mission , we have to use So2 gas to raise the temperature.
( more gas and more smell)

Then adding sulfamic acid in those conditions will not be easy for the operator.We have to try this way once, with or without sulfamic acid.

*Tomorrow I can ask about so2 gas supply,
But I have SMB available now.*

with this condition
(I'm worried about the smell of SO2 gas, the workshop is located in a busy business district)


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## silver1 (May 26, 2022)

Shit! I didn't offer my wisdom just for the hell of it! So in other words education is not the question being ask or sought here, but just give me the answers i'm looking for. Again, this is an art! Yeah my time is more valuable to me than that! If answers and not knowledge, they are different, is all you seek then try the search function. It's all here! I understand frustration, but unless you fix the problem that lead to that frustration this is going to be a viscous circle. Your problem doesn't exist in just one area here, it's exist in all areas. From the equipment your using, to the advice you were given before you got here, all the way down to the inexperience your staff has.

Give a man a fish and he eats for a day. Teach a man to fish and he eats everyday!


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## Geo (May 26, 2022)

As for the sulfamic acid, to answer your question, sulfamic acid destroys nitric acid on a one to one ratio by weight. One gram of sulfamic acid will destroy one gram of nitric acid in solution. As apposed to urea, which does not actually destroy the nitric acid. It binds with nitric acid creating urea nitrate. The operative word being nitrate. Under certain circumstances, the urea nitrate can be broken down and the nitrate will release the stored nitric acid back into solution. I understand that the equipment was not designed to be heated to those temps but perhaps modifications can be made? Perhaps the manufacturer may have an adaptation that can be used.


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## Gold.refinery (May 26, 2022)

I know urea at the end of the wastewater treatment process, reacts with caustic soda to form ammonia. What problem does this cause? 

What are the other benefits of using sulfamic acid over urea? 

Given that we can not heat the tank, what 
problems will occur if I do not use sulfamic acid?


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## Gold.refinery (May 26, 2022)

4metals said:


> Gold Refinery has mentioned using a flocculant. I would like to hear more about what is used and the logic behind it.


We use a flocculat to stick very small particles together. I can ask exactly the chemical of it. 

The manufacturer gave us it, I remember saying that the absorbent powder used in diapers .


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## 4metals (May 26, 2022)

As Orvi pointed out the Sulfur Dioxide is easily handled by your scrubber


orvi said:


> Nox is much difficult to scrubb or destroy. SO2 is acidic, so very simple "basic" absorber with NaOH is usually enough to catch vast majority to acceptable levels.


for this reason I will assume your existing scrubber will handle the Sulfur Dioxide generated either from adding powdered sodium metabisulfite or adding gaseous Sulfur Dioxide. The usual "problem" with fume scrubbers and refining is from NOx, which you have said your scrubber handles well. 

Most refineries I work with have exhaust stacks which extend above the roofline and the fumes released are above their neighbors noses. If you have a stack on a low roof and are a few meters from a neighbors window and at the same level, that's a different story.

That being said you should add the sodium metabisulfite slowly with good agitation. You are agitating by bubbling air, we discussed this before and you know you will have to keep the solution moving. 

Seeing you have a 2" (10cm) exhaust on your precipitation tank, I think your fear of Sulfur Dioxide fume should be from what escapes out the top of the vessel and not out the stack. All the more reason for slow additions.


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## Gold.refinery (May 26, 2022)

4metals said:


> I will assume your existing scrubber will handle the Sulfur Dioxide generated either from adding powdered sodium metabisulfite or adding gaseous Sulfur Dioxide


It will be determined after discussing the scrubber.


4metals said:


> If you have a stack on a low roof and are a few meters from a neighbors window and at the same level, that's a different story.


Unfortunately, the height of the chimney is not high.


4metals said:


> That being said you should add the sodium metabisulfite slowly with good agitation. You are agitating by bubbling air, we discussed this before and you know you will have to keep the solution moving.


Is adding solid SMB different from dissolving in water? 
The gold tank does not have a mixer, if we want to mix the liquid well manually, is that enough? 
how long does it take?
(I think once we have to try with a small volume and observe)


4metals said:


> Seeing you have a 2" (10cm) exhaust on your precipitation tank, I think your fear of Sulfur Dioxide fume should be from what escapes out the top of the vessel and not out the stack. All the more reason for slow additions.


I am waiting for a list of problems with the machine components (Problem with vacuum filters, tank heater, Tank exhaust , scrubber, and other possibilities) to follow up with the manufacturer.


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## Gold.refinery (May 26, 2022)

4metals said:


> I have used sulfamic acid extensively but as Geo mentioned it has always been in heated Phaudler reactors. I think for this application perhaps a hybrid application is in order.


If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat? 
After this, add ice or water and filter the silver chloride.


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## Yggdrasil (May 26, 2022)

Gold.refinery said:


> If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat?
> After this, add ice or water and filter the silver chloride.


Yes you will need heat.
It need to be around 80C for the Sulfamic to react.
Sometimes I wonder if you read your
answers at all??
It is clearly stated in your answers.

If you use either a SO2 tank or a SO2 generator, you can adjust and tinker so
it won’t give off much at all. 
(All SO2 is used before reaching the surface)
If you choose this route, there may not be much use of Sulfamic at all.

I’d recommend you to do some small tests for your self and maybe your staff, with a few grams just to get acquainted with the processes discussed.


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## 4metals (May 26, 2022)

Gold.refinery said:


> If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat?


I believe you will get the temperature you need to use sulfamic acid to kill off the excess nitric if you add it in the tumbler when the last addition of nitric has gone to completion and the reaction is still hot enough. The question is if the reaction is hot enough to begin with. This is something you will have to physically measure. 

Originally I was skeptical about adding sulfamic to the tumbler because it will be difficult to add from the holes you can open up on the end of the tumbler where the exhaust to the scrubber exits. But then I remembered the charging hole. I added a red arrow pointing to the charging hole on a photo Gold Refinery provided.

This hole is where scrap material is added to the tumbler and it is convenient because it is directly opposite the drain hole where the tumbler empties into the filter. If you stop the tumbler with this port on top, it can be opened and you can measure the temperature. If you have 80ºC or close, you can add sulfamic acid there. 

Using the charging hole is good because it will allow you to carefully add the sulfamic and to monitor it closely so it doesn't foam too high. 

Re-read the posts in this thread by Geo and Orvi about adding the sulfamic and add it carefully if it is at 80ºC or higher. do not over-add and look for the signs as described to determine when you have added enough. 

Then you can add ice through the same hole and let the solution cool before filtering. 



Geo said:


> sulfamic acid destroys nitric acid on a one to one ratio by weight. One gram of sulfamic acid will destroy one gram of nitric acid in solution.


This is not as simple as it sounds. It is nearly impossible to know how much of the nitric you added has actually reacted and how much remains in solution. However your working experience can show you the right quantity for subsequent reactions. The nitric (70%) weighs 1.4 grams per ml. You know how many milliliters of nitric you added. Weigh out the quantity of sulfamic acid you will need to neutralize 100% of the acid you used (this will be too much, but it will help you do this properly in the future). Add the sulfamic, paying attention to the way it reacts and stop when it is complete. The activity of the reaction of the sulfamic acid on the solution should provide enough mixing that you need not seal up and spin the tumbler for this part. Simply place the cover over the hole to provide stronger exhaust from the scrubbing duct. 


orvi said:


> Generally, you add sulfamic acid similarly as urea - heat the solution to at least 80 °C, add sulfamic SLOWLY until it stop fizzing (not to foam over), then you wait at least 15 minutes - or better 30 minutes and add little amount and observe if there is some fizzing. If it still reacts, add more and repeat the waiting step.


When you are done, weigh the remaining sulfamic that you haven't used. Now you can calculate what percent of the calculated sulfamic acid you actually used. Do this for a few lots and soon you will have a working value for future use. I would be surprised if it is more than 25% of the calculation made for 100% of the acid added. 

I realize your system has the capability to add peroxide. I have never used peroxide in this fashion and the 4:1 aqua regia quantities I gave you per ounce of material should provide sufficient oxidizer. 

Gold Refiner, please inquire what the wetted parts of the dosing pump provided for peroxide additions are. If compatible, the pump could be used for a slow constant nitric feed which will give you a continuous controlled reaction which could control NOx generation and provide a more constant warming effect for the reaction.


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## Gold.refinery (May 27, 2022)

Several misunderstandings seem to have happened. 
Please look at the two photos I sent. 
We have *4 holes on door* in the top of the tumbler. The central hole is for Fumes to exit and connect to the condenser. 
Two holes is covered with glass , to look at the reaction. 
A hole to add urea or sulfamic acid or…. Also, in the second photo, it is clear that through the outlet pipe, there is a thin hose that is connected to the dosing pump.

After explaining this image, I have to point out that we do not Fill scrap through the valve into the Tumbler, 
we open the door on top of the Tumbler and fill the scrap in the Tumblr . 
We can also use the hole you saw in the picture to measure the temperature of the solution with laser thermometer. Also to add sulfamic acid. 
The valve you mentioned with red arrow , 
we open for the final washing of Tumbler.


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## 4metals (May 27, 2022)

The reason I suggested the charging port (as some manufacturers refer to it) as the place to add and monitor the sulfamic additions is because it is lower than the exhausted end and the fumes are drawn towards the exhaust. Opening a port on the high end will allow fumes to escape more easily. The second reason is the charging port is closer to the solution level and any slight rise from the rate you are adding chemistry will be easier to notice. As far as the chemistry goes, it is the same on each end. 

One thing I have learned from a lifetime of refining is that there are two types of refiners. Refiners who have experienced a run away reaction with loss of values, and those that lie and deny it. If you refine enough it will happen. One general rule of refining is to leave at least 50% of your vessel to accommodate a rise due to chemical additions. If your tumbler reactor is operating at design capacity (25kg) or close, you will not have that 50% for a rise. The reaction will rise and it will produce aerosols of gold containing acid which will rise above the exhaust airflow and be sucked into the condenser circuit. 

In the case of your equipment, if the temperature rise of the reaction gives you the heat to use sulfamic acid, you can CAREFULLY add the sulfamic and closely monitor your additions as the reaction rises. That is the only benefit of adding sulfamic to the tumbler reactor. Urea will work on a cold solution so I would never add it to the tumbler because it bubbles excessively and will cause aerosol losses. This I am sure has happened to you because in the photo you just sent, is an employee with a full scoop of urea just waiting to be poured into the funnel. That is a lot of urea to drop in at once, especially in a reaction vessel where you cannot have a 50% capacity for the reaction to rise. 

This is precisely why you should add chemicals based on the reaction and not off a scripted sheet saying add X. 

The safest option for you will undoubtedly be adding Sulfur Dioxide gas to both de-NOx the solution and drop the gold. 

While you still have urea and sodium metabisulfite you can use the urea in the precipitating tank to de-NOx the solution. (sparingly based on reaction and certainly not in large scoops) followed by additions of sodium metabisulfite while mixing the solution until the gold is dropped. And then mix the dropped gold to be sure you have dropped the gold from the solution hiding under the gold precipitate.


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## Gold.refinery (May 27, 2022)

Excellent ,Points was very effective and useful. Thanks 4metal


4metals said:


> Opening a port on the high end will allow fumes to escape more easily. The second reason is the charging port is closer to the solution level and any slight rise from the rate you are adding chemistry will be easier to notice


I agreed to add sulfamic acid to Tumblr from the bottom valve, because I saw the reaction up close. Question: Is it better to open the door to exit the fumes or is it closed? I think it is open. Right?



4metals said:


> If your tumbler reactor is operating at design capacity (25kg) or close, you will not have that 50% for a rise. The reaction will rise and it will produce aerosols of gold containing acid which will rise above the exhaust airflow and be sucked into the condenser circuit.


There are dimensions of Tumblr: 
Diameter :63 cm , Length : 100cm


4metals said:


> you should add chemicals based on the reaction and not off a scripted sheet saying add X.


I am convinced that seeing the reaction is more important than the values on paper, especially documenting the values in different reactions will be useful to find Amounts.



4metals said:


> While you still have urea and sodium metabisulfite you can use the urea in the precipitating tank to de-NOx the solution. (sparingly based on reaction and certainly not in large scoops) followed by additions of sodium metabisulfite while mixing the solution until the gold is dropped. And then mix the dropped gold to be sure you have dropped the gold from the solution hiding under the gold precipitate.


I will follow up to launch SO2 because it both precipitates gold and de-noxx the solution. 

But before that , I will use SMB, urea. Also sulfamic acid. 
I'm looking to test scrubbers when I use SMB. I will also check the small size of the exhaust above the gold tank in the next operation.


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## Gold.refinery (May 27, 2022)

I have a few days to summarize the problems of Refining machine for a serious follow-up from the manufacturer. 
So far we have reached the stage of gold precipitate . 
I noticed problems in the parts 

*1)* I noticed there is a BIG problem with the filters. There is not enough vacuum space between the floor and the paper or fabric filter, nor is the grid suitable. 

*2)*I noticed that the chimney outlet of the gold tank is weak. 

*3)*I realized that the gold tank needs a mixer, not a hand mixer. 
I realized that the gold tank should have a heating system. 

Of course, we have not study scrubbers, waste treatment system and filter press untill now. 
I hope in the end I can summarize the problems of all parts to follow the manufacturer.


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## Geo (May 27, 2022)

The reaction between sulfamic acid and nitric acid is only violent when the solution is at or near 94°C. The reaction will happen at a lower temp with a much more subdued reaction but the process takes more time. If your reaction vessel is set at a certain volume and there is no room for a more violent reaction, you may have to work with the sulfamic acid to discover the correct temperature and amount to add at one time. 4metals gave you the best process by measuring your sulfamic acid against the nitric acid used. The factors that might change would be temp, amount added at one time and time needed to complete the process.


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## silver1 (May 27, 2022)

Is that a fresh water filter or what is that i have circled?


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## 4metals (May 27, 2022)

Ralph, I believe that is the canister filter that Gold Refinery showed the stannous test on its contents. It's purpose is to catch any silver chlorides that escape the filter labeled Silver Chloride filter. They are difficult to rinse free so in addition to catching silver chlorides it retained a little gold chloride too!


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## 4metals (May 27, 2022)

Gold.refinery said:


> Of course, we have not study scrubbers, waste treatment system and filter press until now.


Please provide photos of your fume scrubber, your waste treatment system and your filter press. 
There are a few technical specifications we need to know about the fume scrubber to evaluate it properly. We need to know the air flow rate through the scrubber, probably expressed in cubic meters per hour. Then we need to know the cross sectional area of the packed section of the scrubber. The packed section is the area that contains the tower packing where the chemical reactions take place. To effectively scrub NOx fumes they have to remain in the "scrubbing zone" inside the scrubber for about 8 seconds. If we know the actual area of the packing and the flow rate we can see if the scrubber has the necessary retention time for effective scrubbing of NOx. Finally, is there a pH controller and dosing pump to maintain the pH of the scrubber liquid? 

I assume you are treating your waste with a process known as classic destruct. This involves adding caustic liquid to the acid waste until the metals. in solution are converted over to. metal hydroxides, these are filtered from the solution in your filter press. The use of urea, and the subsequent smell of ammonia you sensed tends to re-dissolve some of the copper and cause treatment problems, that's one reason why staying away from urea is preferred


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## silver1 (May 27, 2022)

Has he posted any inside pictures of the AgCl filter funnel yet or did i miss them? He is using seperate funnels for the gold powder vs AgCl isn't he?

Yeah i don't like them canister filters exactly for that reason.


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## 4metals (May 27, 2022)

silver1 said:


> He is using seperate funnels for the gold powder vs AgCl isn't he?


One would hope he had one for each but he has not been specific. There's only one thing worse than a filter that doesn't suck well...... that's two filters that don't suck well!


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## Gold.refinery (May 27, 2022)

silver1 said:


> Is that a fresh water filter or what is that i have circled?


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## Gold.refinery (May 27, 2022)

4metals said:


> One would hope he had one for each but he has not been specific. There's only one thing worse than a filter that doesn't suck well...... that's two filters that don't suck well!


Yes, we have three filters but with the problems mentioned. For silver chloride, for gold, for sludge from the mother solution after the precipitation below the secondary tank.


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## silver1 (May 27, 2022)

Gold.refinery said:


> Yes, we have three filters but with the problems mentioned. For silver chloride, for gold, for sludge from the mother solution after the precipitation below the secondary tank.



Dam!


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## Gold.refinery (May 28, 2022)

4metals said:


> is there a pH controller and dosing pump to maintain the pH of the scrubber liquid?



Yes,We have a dosing pump that regulates the pH of the water inside the scrubber. Of course, for the first pair of scrubbers, the second pair of scrubbers do not have pH control with the dosing pump.

In the tank of the first pair of scrubbers, ammonia is added to control the pH of 7. In the tank of the second pair of scrubbers, there is a caustic soda.

The white smoke I mentioned earlier comes out of the chimney (at the peak of the reaction), after the addition of ammonia. The smell of chlorine gives very little.

The electric motor has an inverter to regulate the air flow.


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## Gold.refinery (May 28, 2022)

4metals said:


> I assume you are treating your waste with a process known as classic destruct. This involves adding caustic liquid to the acid waste until the metals. in solution are converted over to. metal hydroxides


Our classic filtration system has 4 stations with the method of adding caustic soda according to the image.
The first station has a motor mixing with the blade. In the first station we add AL.

The second station has pipe with air injection.

The third station has a motor mixer with a dosing pump to add caustic soda.

The fourth station is for final maintenance and control only.


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## Gold.refinery (May 28, 2022)

Finally, the liquid goes by a diaphragm pump to press the filter.


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## 4metals (May 28, 2022)

This thread is getting long and I think it best if I break it off into separate threads, one for fume scrubbing, and one for waste treatment. 

Seeing as it is Memorial Day weekend here in America, my Big Green Egg and a pork roast is beckoning louder than the forum, I will try to split these threads off this weekend and start replies in earnest after the long weekend.

From this point onward it will be best to concentrate on the chemistry of getting your gold as pure as possible in this thread. Gold Refinery, we are still waiting on details of your flocculant. From what you told us we know it is used in baby diapers but maybe a bit more info?


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## silver1 (May 28, 2022)

Sodium polyacrylate ?


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## silver1 (May 30, 2022)

https://www.intechopen.com/chapters/70081


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## Gold.refinery (May 30, 2022)

As you know, to flake off scrap, we use a whirlpool created by pumping water into a steel tank. 
Question: Is water *temperature* important in the process of making scrap grains finer?


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## Gold.refinery (May 30, 2022)

FrugalRefiner said:


> One of our past moderators always used an ammonia wash on his precipitated gold. He dropped his gold from very concentrated solutions, which can hold a bit of silver chloride in solution. He used ice to cool the solution as he added his precipitant. So, he ended up with a bit of silver chloride precipitating with his gold as the solution was diluted and cooled by the ice. He used an ammonia wash do dissolve the silver chloride before melting his gold.
> 
> Another former moderator chose to dilute his pregnant solution to three times the volume. The dilution would cause the silver chloride to precipitate, and he would filter it out before dropping his gold. It creates more waste, but he didn't need an ammonia wash.


*Question:*
I tried both methods, but due to changes in other parameters, I can not judge which method is better. 
Since we do refineries on a scale of 15 to 25 kg, which route do you recommend, ice with less extra water, or adding water double or triple the volume of the solution ?? 
At what time?
Which is better not to pass silver chloride?


Please help me about this, and brainstorm in forum.


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## FrugalRefiner (May 30, 2022)

Unfortunately, I don't have the experience to answer your questions. I've never refined in the volume you are. My suggestion would be to continue to test various methods to find what works best for you.

As you've discovered, changing multiple parameters at the same time is not a good practice, as you can't be sure which changes have had which results. Change one thing at a time. Repeat as needed to confirm what effect the change has had. Then change something else.

Dave


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## 4metals (May 30, 2022)

FrugalRefiner said:


> As you've discovered, changing multiple parameters at the same time is not a good practice, as you can't be sure which changes have had which results. Change one thing at a time. Repeat as needed to confirm what effect the change has had. Then change something else.


If you change too many things at once you will never know which change was the most effective of if some changes made things worse but were masked by another change. 




Gold.refinery said:


> As you know, to flake off scrap, we use a whirlpool created by pumping water into a steel tank.
> Question: Is water *temperature* important in the process of making scrap grains finer?


Cooler water is always better but not necessary to make shots for digestion.

Considering the weight of undissolved compared to the start weights of your reactions this isn't something you should even be worrying about now. A tumbler plant, by moving the material being dissolved against the material it is tumbling with provides a beneficial grinding action which is effective even if you have some larger chunks in the mix.


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## 4metals (May 30, 2022)

Gold.refinery said:


> Since we do refineries on a scale of 15 to 25 kg, which route do you recommend, ice with less extra water, or adding water double or triple the volume of the solution ??
> At what time?
> Which is better not to pass silver chloride?


25 kg lots of karat gold is not exactly large scale refining, but it is something a medium sized refiner will encounter. The colder you can get the solution before filtering it, the larger the effect on the solubility of silver chloride in your solution. You have bigger problems to solve than worrying about 3 times dilution with water or cooling with ice. Both will work well but you have to consider how many gallons of waste do you want to deal with?

Right now you have filters that do not seal properly, and papers too small for the filter area and filters that do not properly de-water whatever you are filtering. Any of these can cause excessive silver chloride in your final product. Fix your filtration before you go chasing a problem that may not exist.


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## silver1 (May 30, 2022)

Im thinking with all the washing and flushing that is done there is more than enough dilution. Water in.. water out. Filteration and washing procedures (HCl ) will eliminate the majority of the chloride problems.


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## AMS-Pro (May 30, 2022)

4metals said:


> 25 kg lots of karat gold is not exactly large scale refining, but it is something a medium sized refiner will encounter. The colder you can get the solution before filtering it, the larger the effect on the solubility of silver chloride in your solution. You have bigger problems to solve than worrying about 3 times dilution with water or cooling with ice. Both will work well but you have to consider how many gallons of waste do you want to deal with?
> 
> Right now you have filters that do not seal properly, and papers too small for the filter area and filters that do not properly de-water whatever you are filtering. Any of these can cause excessive silver chloride in your final product. Fix your filtration before you go chasing a problem that may not exist.


I'm definitely with 4metals on this. Too many current issues with the filter setup to be able to have proper data. Preplanning is good, but the current setup needs to be properly running to know where to go, and if the data is still the same once the filtration issue is fixed.

As far as the silver chloride in general, forget the ammonia wash.... Dilute your solution when hot, then cool it down, and then properly filter is the name of the game in your instance.

As an alternative that's a bit newer, and recyclable, the use of Diamide L to precipitate gold is making its way onto the scene. This is something that more than one of my clients has recently been looking into, you may want to as well if you haven't already.

You can find out more about it in the Edinburgh Research Explorer titled : *Tuneable separation of gold by selective precipitation using a simple and recyclable diamide. *At the least, it is worth the read and knowledge.


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## orvi (May 31, 2022)

silver1 said:


> Im thinking with all the washing and flushing that is done there is more than enough dilution. Water in.. water out. Filteration and washing procedures (HCl ) will eliminate the majority of the chloride problems.


Somewhere at start, Gold.refinery said they are diluting the dropped gold to 995... So purity isn´t particularly concerning. Good dilution before filtering and good wash with HCl must bring it past 995 easily.

You are right with water, when it all adds up... Sometimes you end up in quite a volume. And if your worker is diligent enough, it cannot fit the precipitation tank 
But for the dilution effect, water needs to be added before filtering. After filtration, only thing that could help is to add HCL - and let the solution to warm. That will bring some more AgCl to the solution.


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## silver1 (May 31, 2022)

Packing the filter would help here. Run 10 liters, Then put that back in the 50, recirculate it. Proceed from there again filtering. This is called packing the filter. Once the filters packed the solution is usually good to go. This saves any secondary filters the load. If you do a single pass then you will have fine contaminates in your solution.


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## orvi (May 31, 2022)

silver1 said:


> Packing the filter would help here. Run 10 liters, Then put that back in the 50, recirculate it. Proceed from there again filtering. This is called packing the filter. Once the filters packed the solution is usually good to go. This saves any secondary filters the load. If you do a single pass then you will have fine contaminates in your solution.


Yup, exactly. I just clear it out for Gold.refinery, that we mean you pass the solution at least twice through THE SAME filter. 
In the first filtration, you quite often obtain opalescent or merky solution. But if you pass the filtrate through the same filter, it will come out much more clear, if not crystal clear. Reason is that small particles clog the bigger pores and holes in the filter paper/fabric/medium = they pack the filter. So the vast majority of particles cannot fit the other remaining holes and stay on the filter.


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## 4metals (May 31, 2022)

orvi said:


> Yup, exactly. I just clear it out for Gold.refinery, that we mean you pass the solution at least twice through THE SAME filter.


As the system is set now there is permanent fixed piping to run to the precipitation tank. Adding a tee and a flex hose to pump back into the tumbler will facilitate this step. 

First address the issues with the filter.


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## Gold.refinery (May 31, 2022)

In the previous operation, after filtering the silver chloride, we removed the silver chloride from the fabric filter, but did not wash the fabric filter completely. 
Is this enough to better filter or is it wrong?


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## 4metals (May 31, 2022)

The fabric filter is more a filter support than a filter. But it should be rinsed completely each use. The pore size on the fabric is much greater than the pore size on your filter paper.


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## Gold.refinery (May 31, 2022)

since we have to make changes step by step to record the results, to make the right judgment. 
So maybe we should continue the De-Nox step with urea. 
Where is the best place to add urea? Gold tank?


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## 4metals (May 31, 2022)

Gold.refinery said:


> Where is the best place to add urea? Gold tank?


If by gold tank you mean the tank you precipitate the gold in, yes. Adding it in the tumbler will cause aerosol mist containing values to suck up the exhaust duct. In the precipitation tank you can easily see the reaction and judge when it is complete. And have ample room for the reaction to rise.


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## Gold.refinery (May 31, 2022)

you recommends using a prescreen in the center of the filter to collect silver chloride more easily. 
Does not the accumulation of silver chloride keep the liquid containing gold in the center of the filter? 
Also, do you recommend using this on the gold filter to collect in the center of the filter?

To what extent are we allowed to wash silver chloride on the filter? 
Does extra washing cause silver chloride to pass into the solution? (with good filtering ,No)


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## Gold.refinery (May 31, 2022)

Our sedimentation tank does not have a mixer to stir the solution when the gold precipitates. 

Because if we want to stir the solution from the top of the tank manually, SO2 gas (unbearable for the operator) will definitely come out, if we do not stir, the gold drop operation will be difficult. 
What should be done to completely prevent the release of SO2 gas?


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## silver1 (May 31, 2022)

I never neutralize my solutions while still in a vessel with the materials. Once the acid is neutralized cementation will start on any undigested portions left. Always separate first. 

In my shop i have a diaphragm pump mounted to a roll around table/cart. Something like 4Metals mentioned with a rolling filter. The pump has two hoses, each with a 2 ft pvc tube attached at the end of the hose. That way i can stick it in down into about anything. Each hose is 10 ft long, both on intake and exit. Setting that somewhere in my shop i can reach a 20 ft radius. You never know when something may break down or why you might need to transfer something, but when you do it's handy.


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## 4metals (Jun 1, 2022)

Gold.refinery said:


> What should be done to completely prevent the release of SO2 gas?


Add the reagent slowly to control the release and increase the diameter of the exhaust pipe because as it stands now you don't have sufficient air exhaust. 


From the picture you provided and the layout you provided I see some things that concern me. First the 3 tanks are up against a wall so you cannot walk behind them. And the cover is hinged so the back opens not the front. The front quarter is where the exhaust blower attaches and the back 3/4 opens. When the opening is large, it's hard to minimize the escape of fumes. With the back opening your operator is hanging over the equipment to access the opening. 

The section that opens should be the smaller 1/4 that has the fixed plumbing and exhaust. The exhaust should be to the rear, as should the feed pipes. Then the operator can stand in front of the system, peer into the viewing port, and open the smaller lid quickly to add chemicals all without having to hang over the tank to access the opening.


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## 4metals (Jun 1, 2022)

Gold.refinery said:


> you recommends using a prescreen in the center of the filter to collect silver chloride more easily.
> Does not the accumulation of silver chloride keep the liquid containing gold in the center of the filter?


The pre screen is a mesh screen that allows fine silver chloride to fall through and catches larger chunks that have encrusted the undissolved gold. It does not trap any pools of liquid. The screen makes your job easier to separate the silver chloride encrusted undissolved chunks from the bulk of the silver chloride. Usually the largest share of undissolved gold is larger encrusted chunks and you want those quickly to eliminate considering them as a loss. 


Gold.refinery said:


> Also, do you recommend using this on the gold filter to collect in the center of the filter?


No because all that comes out of the precipitation tank is gold sponge and there is no need to pre screen it. 



Gold.refinery said:


> To what extent are we allowed to wash silver chloride on the filter?
> Does extra washing cause silver chloride to pass into the solution?


Wash the silver chloride until it does not test positive for gold chloride which is in solution. Wash it with cold water to minimize solubility.


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## AMS-Pro (Jun 2, 2022)

How much working space do you have available from the filter canisters on the floor, to wherever the person was standing to take the picture?


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## 4metals (Jun 2, 2022)

Gold Refinery posted this layout. So I assume he could move them out from the wall.


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## AMS-Pro (Jun 3, 2022)

I wonder how accurate that C.A.D. is, but it gives good idea.

Looking at the actual picture, it appears there may be about 9 in. to 1 ft. clearance in between the tanks and the wall. Using the tread depth on the stairs in the picture, and assuming the tread depth is within a range for a human foot to use it, we can figure it to be about 8 in. - 9 in. deep.

I would say it's possible to bring the tank, and tank pedestals away from the wall about 15 in. and install a 2 ft. wide catwalk for access for the rear. This will save some headache with rerouting a bunch of plumbing, and only require slight modification of fume plumbing above what the picture shows. Possibly a longer section of the horizontal supply pipe between tank two, and three (the right two tanks). A smaller access to add chemicals could be drilled in the large lid section using a hole saw/bit rated for metal, weld a threaded stack over that, and use a spring cap (like an oversized gas cap, or something you would see on a semi tractor fuel tank.). The hole would be 3 in. - 4 in. in diameter, and I would center it left or right, between the view window and the the outside edge of the lid. As most people tend to be right hand, I would say the right side would be the better option for comfortability.

The filter canisters would have to be slid further underneath the pedestals after the setup is brought out a bit from the wall, but you would not lose in the walking space from the side the picture was taken, and now you'd also have a 2 ft. cat walk for access behind it as well. I'm assuming the stairs were there for that already, but having a 2 ft. catwalk would surely make it easier, and safer.

The layout could certainly be improved a bit more drastically, however with cost, and relocate some of the larger equipment entirely, but that seems a bit unnecessary at the moment.


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## AMS-Pro (Jun 3, 2022)

A rough idea on just moving the equipment around. Obviously exact placement would have to be fine tuned for adequate working space, but this would be the general idea. 

Edit: I had wrong picture inserted. This is the right picture. 

After giving it some thought, and seeing actual pictures of the layout as opposed to the C.A.D. in corresponding threads, I feel you could actually pull the pedestals out much farther. Enough so that you could actually just rotate them 180 degrees and still use the same fume plumbing without modification. You may have to slightly modify the supply plumbing though.


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## Gold.refinery (Jun 4, 2022)

*Some questions about using SMB:*

Is it better to add SMB in powder or water solution? Cold or hot? 

Is the temperature of the solution containing gold chloride important to add SMB or not? 

Is the pH of the solution important or not? 

How long will it take for the SMB to precipitate the gold? (Compare with Hydz)
(My previous experience with Hydz was about 15 minutes)

Remember, 4metal advised to digest scrap at Tumbler overnight, and precipitation gold in the morning Then melt at noon. 
Will gold complete sediment with SMB at this time?


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## Gold.refinery (Jun 4, 2022)

There is still some hydrazine left in the workshop already. 
If we want to finish it and use it to precipitate gold. 
Is it necessary to add urea for De-Noxx or not?


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## Gold.refinery (Jun 4, 2022)

AMS-Pro said:


> *Tuneable separation of gold by selective precipitation using a simple and recyclable diamide. *At the least, it is worth the read and knowledge.


I have heard about the precipitation of gold with *1)hydroquinone* and *2)hydrazine sulfate*. I'm very interested in discussing this topic.


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## 4metals (Jun 4, 2022)

Gold.refinery said:


> There is still some hydrazine left in the workshop already.
> If we want to finish it and use it to precipitate gold.
> Is it necessary to add urea for De-Noxx or not?


If you feel the need to use the hydrazine you could use it to convert your silver chlorides as well.


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## 4metals (Jun 4, 2022)

Gold.refinery said:


> I have heard about the precipitation of gold with *1)hydroquinone* and *2)hydrazine sulfate*. I'm very interested in discussing this topic.


You’ve gotten everyone participating in this thread rolling their eyes right now! 

For your own good and success of your operation concentrate on using proven methods as have been outlined here before you begin experimenting with different methods.


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## Gold.refinery (Jun 4, 2022)

4metals said:


> If you feel the need to use the hydrazine you could use it to convert your silver chlorides as well.


How is it used?

What is your opinion about SMB Questions?


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## 4metals (Jun 4, 2022)

Gold.refinery said:


> Is it better to add SMB in powder or water solution? Cold or hot?


Powder and temperature doesn’t matter



Gold.refinery said:


> Is the temperature of the solution containing gold chloride important to add SMB or not?


The solution temperature should be cool from filtration but the urea reaction will warm it. Temperature is not critical but cooler is better.



Gold.refinery said:


> Is the pH of the solution important or not?


The pH of the solution after you have de-NOxed it is fine. Do not try to alter it.



Gold.refinery said:


> How long will it take for the SMB to precipitate the gold? (Compare with Hydz)
> (My previous experience with Hydz was about 15 minutes)


Once the solution has no free nitric the reaction is rapid.



Gold.refinery said:


> Remember, 4metal advised to digest scrap at Tumbler overnight, and precipitation gold in the morning Then melt at noon.
> Will gold complete sediment with SMB at this time?


Yes. Remember even if the gold has not settled, of which most of it will have settled anyway, you are filtering this solution and the filter (if you have made the improvements suggested) will catch the fines.


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## 4metals (Jun 4, 2022)

Gold.refinery said:


> How is it used?


Before I give you the method, I should point out one major omission I see in your refinery layout. That is the lack of a hood in which you can carry out reactions safely. This method, as well as potentially using ammonia on gold sponge and many other steps you may wish to try, is not something to do in a bucket on the floor in the middle of the shop. A simple hood with exhaust, both scrubbed and fugitive, is important for both your experiments in learning refining and your long term health. 





Reducing silver chloride w/ NaOH and Hydrazine

Wash this solution thoroughly, several times with distilled water till the pH paper shows mildly acidic and drain the water.

Next add 10% Sodium Hydroxide solution prepared with Distilled water and the white silver chloride turns blackish during addition of Sodium Hydroxide. Mix very very thoroughly & keep adding Sodium Hydroxide until the entire solution turns blackish & there are no white particles of Silver left in the solution.

Make a solution of 10-15% Hydrazine Hydrate with the distilled water and add gradually to the Black solution, the solution will fizz and you will see the Pure Silver rising to the surface. Keep adding 10-15% HH to the solution until the fizzing stops. Let Cool and start washing until the pH paper shows very mildly acidic. 

Dry and heat to convert to Powder, and once dry Melt in Induction melter by adding a pinch or two of Boric Powder to get Pure 99.9+% silver.

Remember the first time through your Silver Chloride will contain undissolved Gold which you want to recover. Obviously the Silver will not be high purity. 
The Silver Nitrate solution you get after dissolving the first run in nitric acid to recover the Gold is filtered and salt is added to the solution to drop the silver as Silver Chloride. This cleaner Silver Chloride you are starting with will produce the 99.9+% Silver for you to sell. 

Remember what I said at the outset. Do this in a hood!!!!!


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## 4metals (Jun 4, 2022)

AMS-Pro said:


> I would say it's possible to bring the tank, and tank pedestals away from the wall about 15 in. and install a 2 ft. wide catwalk for access for the rear. This will save some headache with rerouting a bunch of plumbing, and only require slight modification of fume plumbing above what the picture shows. Possibly a longer section of the horizontal supply pipe between tank two, and three (the right two tanks). A smaller access to add chemicals could be drilled in the large lid section using a hole saw/bit rated for metal, weld a threaded stack over that, and use a spring cap (like an oversized gas cap, or something you would see on a semi tractor fuel tank.). The hole would be 3 in. - 4 in. in diameter, and I would center it left or right, between the view window and the the outside edge of the lid. As most people tend to be right hand, I would say the right side would be the better option for comfortability.


As AMS Pro says you will benefit from access to both sides of these tanks. They are made to be loaded and have chemicals added from the front side which unfortunately has the larger opening, causing fumes to escape because the exhaust is minimal to begin with.

A smaller access port will minimize fume leakage and, it is difficult to tell from the photo's, the viewing port on the top center may actually swivel to allow you to add chemicals there. Although it would be preferable to be able to see the reaction and add at the same time. By being able to view any reaction while slowly adding reagent would be the best option, keeping in mind one of the biggest mistakes made by refiners is over addition of reagents.

But access from the front, where you are not leaning over the exhaust duct and plumbing, would be better.


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## Palladium (Jun 4, 2022)

Something i was wondering about.... I also caught no fume hood, i was wondering.... does that room have a secondary exhaust fan for emergency blow downs to vent the room or is the only exhaust through the scrubber system.


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## 4metals (Jun 4, 2022)

One of the reasons I do not like “dedicated” refining systems is that they are set up for processes to go from tank A to tank B etc. If you do it exactly as it was designed to accommodate the exhaust is sufficient. But there is no accommodation for other processes which, as we can see at Gold Refinery, are really part of the necessary overall process. 
A series of changeable blast gates can switch between ducts to accommodate changes allowing a hood with scrubbed drops. I prefer to set up a facility with scrubbed drops to scrub fumes generated and what is called fugitive emission which is a non scrubbed direct exhaust which evacuate any wisps of fume escaping the scrubbed drops and overall makes the work space more pleasant for the operator.


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## Palladium (Jun 4, 2022)

Later on i assume he's going to switch from NaOH/ Hydrazine to NaOH/ sugar?

Another thing i was thinking you might need to explain is the flow process. This has to be calculated in the process just like the flow is calculated in the waste stream. This will add to the waste stream, but what i mean is he said he was planning on running 25 kg daily with i believe a 6.8 % silver feed? That's producing about 3.5 lbs of silver chloride a day. X 5 days = 17.5 lbs per week. I guess he could do smaller lots to keep up with it, but to me that's working myself to death. On the flip side if you don't do it in smaller lots it can be a a little harder in larger volumes, but doable if done right. Where are these conversions going to be done? Not in the tumbler you do gold in i assume? It could be i guess, but would require a lot of cleaning between bases and acids. I'm thinking of the agitation here. If it's done in that holding tank i don't think that mixer, don't know, would be enough to chop the chlorides up enough. You need something really fast and vigorous to keep those chlorides stirred or they just lay down on the bottom. Just a lot of questions i guess. You thought that gold was a pain in the ass! I do things a little different though, 4Metals do you see what i'm talking about?


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## Gold.refinery (Jun 4, 2022)

Palladium said:


> Where are these conversions going to be done?


What do other members think about using Tumbler AR for soda-caustic and silver operations?
What is the maximum volume of silver chloride that the process can control?


Palladium said:


> If it's done in that holding tank i don't think that mixer, don't know, would be enough to chop the chlorides up enough


Which Tank? Do you mean First waste water Tank with Mixer?? 


Palladium said:


> You need something really fast and vigorous to keep those chlorides stirred or they just lay down on the bottom


If I do it in small amounts, I can use Stirring Hot Plate. do you agree?


----------



## 4metals (Jun 4, 2022)

Don't even think about converting the chlorides in the tumbler, it cannot handle the volume of solids you will have to drain. 

The best results I have ever had are in a polypropylene plastic cement mixer with no internal metal parts. If you can get a model that allows you to add a rheostat to slow the RPM down even better. They hold a lot of volume, they are easy to drain into the filter, and a flex pipe going to a scrubbed exhaust on a loose fitting cover allows it to spin and exhaust. I have used these to process lots up to 300 ounces of silver chloride.



Truth of the. matter is one of these tumblers can do everything the gold refining tumbler they have is doing.


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## 4metals (Jun 4, 2022)

Palladium said:


> That's producing about 3.5 lbs of silver chloride a day. X 5 days = 17.5 lbs per week.


A nice small silver cell producing about 300 oz a week (40 oz a day) would solve the recovering the gold from the chlorides and dissolving twice issue. Smallest professionally made Silver cells produce 3000 oz a week. Small footprint and will run exceptionally well with silver reduced from chlorides with no copper to foul the electrolyte.


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## Gold.refinery (Jun 4, 2022)

4metals said:


> A nice small silver cell producing about 300 oz a week (40 oz a day) would solve the recovering the gold from the chlorides and dissolving twice issue.


Good idea


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## AMS-Pro (Jun 5, 2022)

Gold.refinery said:


> I have heard about the precipitation of gold with *1)hydroquinone* and *2)hydrazine sulfate*. I'm very interested in discussing this topic.


Lord, you should put those two in the same boat with Ammonia and just forget about it. Hydrazine can be explosive, you don't need that in your life.


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## AMS-Pro (Jun 5, 2022)

4metals said:


> A nice small silver cell producing about 300 oz a week (40 oz a day) would solve the recovering the gold from the chlorides and dissolving twice issue. Smallest professionally made Silver cells produce 3000 oz a week. Small footprint and will run exceptionally well with silver reduced from chlorides with no copper to foul the electrolyte.
> 
> View attachment 50572
> View attachment 50573


This is a beautiful piece of equipment, with such a small footprint too.


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## Shark (Jun 5, 2022)

> Take me down to the Paradise City, where the coffee is hot, and the gold is pretty. Ohhh, can we please, refine gold.
> Sing to the tune of "Paradise City".
> Now it's stuck in your head too.
> You're welcome.


Yep, now it's stuck there.....


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## AMS-Pro (Jun 5, 2022)

Shark said:


> Yep, now it's stuck there.....


You're the first to comment on that. It was the end of a long day, cleaning out the electrowinning machines. Radio was on a classic rock station, and had some coffee to keep me awake, it was just one of those things. It's kind of a ritual now.


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## Shark (Jun 9, 2022)

Quick question that might sound odd and may have been posted somewhere that I missed…. What are these made from? Coated metal or some sort of plastic?


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## AMS-Pro (Jun 9, 2022)

Shark said:


> Quick question that might sound odd and may have been posted somewhere that I missed…. What are these made from? Coated metal or some sort of plastic?


What are you referring to, the silver cell 4metals posted?


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## Shark (Jun 9, 2022)

The AR reactor. I am assuming it’s some type plastic but assuming causes to many problems.


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## AMS-Pro (Jun 9, 2022)

My first guess would be an epoxy paint of some sort.

My second guess would be a PTFE coating.


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## 4metals (Jun 9, 2022)

Shark said:


> The AR reactor. I am assuming it’s some type plastic but assuming causes to many problems.


The one on the photo appears to be PVC but there are manufacturers in Türkiye who make them out of titanium which making heating them possible.


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## AMS-Pro (Jun 9, 2022)

To me, it looks to be a coating on this system. If the frame has the same paint, from this angle, it looks like the paint was running on the upper left of the frame. Also the difference in color/reflection between the pipe and the plate it connects to. The hinges are welded on the access panel, as well. Maybe OP can tell us, it would be on the spec sheet for the equipment.


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## AMS-Pro (Jun 9, 2022)

Shark said:


> The AR reactor. I am assuming it’s some type plastic but assuming causes to many problems.


Now you've got me wondering about something trivial during the middle of my morning coffee. 

Payback for the paradise quote, touché.


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## 4metals (Jun 9, 2022)

I suppose Gold Refinery could walk over to it and knock on it. That should tell the story, metallic or plastic.


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## Gold.refinery (Jun 9, 2022)

AMS-Pro said:


> To me, it looks to be a coating on this system. If the frame has the same paint, from this angle, it looks like the paint was running on the upper left of the frame. Also the difference in color/reflection between the pipe and the plate it connects to. The hinges are welded on the access panel, as well. Maybe OP can tell us, it would be on the spec sheet for the equipment.


The components that are directly related to the acid are all PP. 
Structures are metal that has been painted and covered with PP.


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## AMS-Pro (Jun 10, 2022)

Gold.refinery said:


> The components that are directly related to the acid are all PP.
> Structures are metal that has been painted and covered with PP.


So for clarification, the reactor is solid PP, and is not metal with a PP coating?


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## 4metals (Jun 10, 2022)

I have never seen a tumbler system made as coated or laminated metal. Probably because the threat of de-lamination with use.

The only coated metal vessels I’ve worked with are glass lined Phaudler reactors, but that’s an entirely different class of equipment. 

Gold Refinery was due to either meet with or speak to the manufacturer about modifying some of the equipment. I wonder how that was received?


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## Shark (Jun 10, 2022)

I hope he shares that with us. This had been a very enlightening post for me. I am sure there are others that have learned from it as well.


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## AMS-Pro (Jun 11, 2022)

4metals said:


> I have never seen a tumbler system made as coated or laminated metal. Probably because the threat of de-lamination with use.
> 
> The only coated metal vessels I’ve worked with are glass lined Phaudler reactors, but that’s an entirely different class of equipment.
> 
> Gold Refinery was due to either meet with or speak to the manufacturer about modifying some of the equipment. I wonder how that was received?



I was thinking more of a titanium tumbler reactor, that just happened to be painted with an epoxy paint/PTFE coating, or in the OPs case PP-H to match the surroundings/ease of cleaning.


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## billgold (Jun 11, 2022)

Gold Refinery appears to have equipment that was designed for one specific refining path - which unfortunately has not defined by the manufacturer. For the process paths we normally use, the equipment seems to be marginal at best - such as the relatively useless stock filters and lack of adequate worker protection from fumes.

To complicate matters, I don't think that Gold Refining really understands the basic refining process, nor how to tell when one step is completed and that it is time to move on to the next. Nor does he appear to know how to tell when something is not proceeding correctly or how to recover from problems.

I personally think Gold Refinery would profit greatly by spending a few months with CM Hoke's book (plus the library) and running a bunch of small batch refining jobs. As others have stated before refining is as much an art as a science - especially when you need to minimize costs in materials and time. Without a thorough understanding of what is going on - neither labor or material costs can be minimized. 

Nor has this discussion been particularly orderly or thorough, despite efforts to keep the discussion focused. For example, I have seen nothing on the composition of the feed stock nor what needs to be done in preparation for the AR digestion - if indeed, that should even be the first digestion step.


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## Gold.refinery (Jun 12, 2022)

billgold said:


> I don't think that Gold Refining really understands the basic refining process, nor how to tell when one step is completed and that it is time to move on to the next. Nor does he appear to know how to tell when something is not proceeding correctly or how to recover from problems.


Exactly



billgold said:


> running a bunch of small batch refining jobs


We are doing this.

I will share as soon as the reports are completed. 

(Of course, due to equipment defects, changes and suggestions from members are not quick.)


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## EMRE (Jun 12, 2022)

4metals said:


> I believe you will get the temperature you need to use sulfamic acid to kill off the excess nitric if you add it in the tumbler when the last addition of nitric has gone to completion and the reaction is still hot enough. The question is if the reaction is hot enough to begin with. This is something you will have to physically measure.
> 
> Originally I was skeptical about adding sulfamic to the tumbler because it will be difficult to add from the holes you can open up on the end of the tumbler where the exhaust to the scrubber exits. But then I remembered the charging hole. I added a red arrow pointing to the charging hole on a photo Gold Refinery provided.
> View attachment 50347
> ...


4metals

that charging hole may very well be under the water after all the acid was charged. Only if those Turks made that hole a bit further up! O))))


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## EMRE (Jun 12, 2022)

Geo said:


> The reaction between sulfamic acid and nitric acid is only violent when the solution is at or near 94°C. The reaction will happen at a lower temp with a much more subdued reaction but the process takes more time. If your reaction vessel is set at a certain volume and there is no room for a more violent reaction, you may have to work with the sulfamic acid to discover the correct temperature and amount to add at one time. 4metals gave you the best process by measuring your sulfamic acid against the nitric acid used. The factors that might change would be temp, amount added at one time and time needed to complete the process.


may I ask a stupid question;
I thought nitric boils around 85c. how come there is nitric available at 94c?


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## EMRE (Jun 12, 2022)

4metals said:


> The one on the photo appears to be PVC but there are manufacturers in Türkiye who make them out of titanium which making heating them possible.


all from polypropylen


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## Geo (Jun 12, 2022)

EMRE said:


> may I ask a stupid question;
> I thought nitric boils around 85c. how come there is nitric available at 94c?


It is not an instantaneous reaction decomposing acid with heat. It takes quite a long time to decompose nitric acid with just heat. Sulfamic acid needs the heat to drive the reaction forward. That is the temp the reaction is at it's most violent. In practice, you do not want to heat the solution that hot to add sulfamic acid.


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## EMRE (Jun 12, 2022)

Geo said:


> It is not an instantaneous reaction decomposing acid with heat. It takes quite a long time to decompose nitric acid with just heat. Sulfamic acid needs the heat to drive the reaction forward. That is the temp the reaction is at it's most violent. In practice, you do not want to heat the solution that hot to add sulfamic acid.


thanks, I have one more;

we provide diamond removal service and we run titanium reactors. I always keep the AR temperature around 75c thinking of avoiding boiling. with the information you provided above, what temperature would you recommend? we have 5 hours turnaround time start to finish. I always look for ways to speed it up.


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## orvi (Jun 12, 2022)

Gold.refinery said:


> Exactly
> 
> 
> We are doing this.
> ...



So, if I remember correctly, we pointed out few culprits, where gold could be hiding:

1. retention of gold solution in the system, mainly in some filter parts, which were pointed to be badly designed for the purpose, they should serve
2. incomplete precipitation of gold, which could be found in the second tank sludge (with XRF) after cementation
3. gold being locked up in silver chloride sediment after dissolution in AR

Gold.refinery, what was done with these issues ? Did we improve the yield ? or gold is still escaping. Were some parts of instruments reorganized/altered to better serve their purpose ?

I only want to know, if we are going somewhere.


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## Geo (Jun 12, 2022)

EMRE said:


> thanks, I have one more;
> 
> we provide diamond removal service and we run titanium reactors. I always keep the AR temperature around 75c thinking of avoiding boiling. with the information you provided above, what temperature would you recommend? we have 5 hours turnaround time start to finish. I always look for ways to speed it up.


When I am working, I don't usually have my IR thermometer handy so I don't have an exact temp. I normally go by touch. I heat the solution until the beaker is slightly too hot to touch the beaker. If I had to guess, I would say between 46°C and 50°C. Just too hot to touch the beaker. Any higher than that and you risk a boil over.


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## 4metals (Jun 12, 2022)

Geo said:


> If I had to guess, I would say between 46°C and 50°C. Just too hot to touch the beaker.


I was under the impression that the touch method was a bit warmer than you have experienced. This chart I found indicates time for a 3rd degree burn.

48ºC is 118ºF for reference. I shower with water warmer than that. 

Maybe a thermometer can give more reliable data? 94ºC is 201ºF!

​
Water
Temperature​Adults
(_skin thickness of 2.5 mm_)​Children 0-5 Years
(_skin thickness of 0.56 mm_)​<160°F​1 second​–​<149°F​2 seconds​0.5 seconds​<140°F​5 seconds​1 second​135°F​10 seconds​4 seconds​133°F​16 seconds​–​<130°F​35 seconds​10 seconds​127°F​1 minute​–​125°F​2 minutes​–​124°F​3 minutes​–​120°F​10 minutes​–​


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## EMRE (Jun 12, 2022)

4metals said:


> I was under the impression that the touch method was a bit warmer than you have experienced. This chart I found indicates time for a 3rd degree burn.
> 
> 48ºC is 118ºF for reference. I shower with water warmer than that.
> 
> ...


I control the reactions with dipstick thermometer. I keep it around 75c. I thought I would loose the nitric above that. Touch is the way to go too. 45c is outside temperature in summer in some counties. too low for our work in my opinion.. My original idea was, if I heat AR to its maximum limit, would it penetrate through Agcl crust on the jewelry and dissolve better or faster?


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## 4metals (Jun 12, 2022)

Your reactors are static and silver chloride build-up is worse in static reactions. The entire benefit of the tumbler reactors is the tumbling of the vessel breaks away the chloride crust. Not sure how it would affect the speed of the reaction (it should help) but the manufacturers of tumbler plants claim you can process alloy with higher Silver due to the mechanical advantage in breaking up those chlorides. In stone removal, where you cannot alloy lots together to get silver lower, this advantage may be substantial in minimizing undissolved chloride encrusted chunks.


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## Geo (Jun 12, 2022)

Maybe I'm just a big softie.  I do increase the heat as I go. That way I ensure the nitric has been depleted. If you stop heating while still getting any kind of reaction, even a very subdued reaction means there's still free nitric acid. The reason I don't start adding while hotter is the real possibility of a boil over. 

I generally follow the same process I use for formic acid conversions. Gradual increases in heat the whole time.


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## orvi (Jun 12, 2022)

My professor on university said good organic chemist must hold 100°C vessel in hand  
Yeah, that´s right. Any kind or reactionin AR when warm or hot means the active species are there. It is completely possible that after 1/2hour or so, there is no nitric acid in chloride solution, if it is hot and diluted enough. But dissolved chlorine, NOx-gasses and NOCl like species persist. That is why when you take the pot off the heat in the evening and let it cool overnight to room temperature, it is usually enough to add 2-3 spoonfuls of sulfamic to kill all active species, even for 1,5-2 liters of pregnant AR. AR deplete it´s oxidizing capacity at elevated temperature even if no metal is added to it. To the point of solubility of chlorine, NOx gasses and NOCl-like species at that temperature. 
That is the reason why it is wise not to boil things in AR (if good reagent economy is desired), because loss of oxidizing power in Cl2 evaporation is very big.


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## Gold.refinery (Jun 12, 2022)

We performed a new refining operation and applied some of the recommendations mentioned in this forum. 

Obviously we could not implement all the recommendations due to device problems (until they are fixed soon)

I try to explain the process step by step, with the changes applied in each step



We prepared a reliable feed with the following analysis:

Au:755.4

Ag:57.4

Cu:164

Zn:11.2

Fe:0.6

Ni:4.8

Cd:6.4



Feed weight 2859.8 gr. equivalent to 750 carat.

*Melting and Flaking :*

We melted all the scrap in one step (for the homogeneity of the percentage of silver in the gold beads), then we emptied the melt into water at 2 ° C and flake it well. Then we dried and weighed. *2.2 grams* of gold was not obtained after smelting and flaking operations. I must say that we used boric acid before melting to cover the graphite crusible.



*Scrap digestion , Gas purification with scrubbers:*

According to the calculations, we should add 2.4 lit nitric acid and 9.8 lit hydrochloric acid. 

First we added 8 liters of HCl and 1 liter of HNo3. After about an hour, we added another 1 liter of nitric. After one hour, we added 0.5 liters of HNo3 and 1.8 liters of HCl. 

We did not use hydrogen peroxide in this reaction, but in the past we added it using a dosing pump. 



After an hour of reaction, we turned on the Tumbler rotating.



The reaction subsided after about 4 hours and 30 minutes. The amount of undissolved seeds was *23.15 gr.



Scrubbers:*

Fortunately, we have removed ammonia from the scrubbers. It was great. 

We have four scrubber towers that pump water from two tanks to purify gases. We set the pH in the first tank to 10.5 with a dosing pump and a concentrated caustic soda solution. We also manually set the second tank of scrubbers to ph 10.5. 

At the beginning of the reaction we had some fume at the end of the chimney, but by adjusting the airfan flow with driver, all the fumes was removed completely. When the airfan motor frequency was between 9 and 15, we had no odor or fumes in the chimney. 

When the frequency was set above 25, we had some odor and steam at the end of the chimney. 

When the frequency was less than 8, gas was released into the room.

We set the frequency at 18 at the peak of the reaction and 10 when the reaction calmed down.



*Diluting, Cooling and Filtering AgCl:*



After the reaction subsided, we added 3 liters of ice and allowed the solution to cool. We did not add extra water at this stage. (In the past we used to add water). 

Unfortunately we could not modify the previous filters here. But we used a fabric filter and two paper filters to cover the gaps. 

(In the case of gold filtration, we did better, we filtered with the italimpianti filter, I will explain later)
We filtered the solution and the silver chloride remained. We washed the Tumbler and valves completely.

Rinse the silver chloride with cold water until the soluble stannous chloride test is negative. 



We have not removed the cylindrical filter yet, the stannous test was negative, the color of the filter was not gray, ie the silver chloride was filtered.



We also collected unresolved gold beads. 

23,15 gr.



We wash the silver chloride filter and store it in gallons of chloride with some water.



*DeNOxx:*
(we could not heat the solution, so we could not use sulfamic acid)

After the clear golden green solution was transferred to the first tank, we added a little water. Then we slowly added the urea and stir it.

We added about 600 gr.of urea. 

At first it was completely reactive and solvable. Finally, the urea seeds reached the bottom of the tank, so that it felt unresolved in the bottom of the tank.  (But we still have doubts about the amount of urea seen by the reaction)



*Precipitation:*
We know the best precipitator is so2 gas, and the next option is smb. We prepared ourselves to use SMB, unfortunately we did not use it in this process for two reasons, first, our tanks do not have a chimney for 24-hour ventilation, our first tank does not have a mixer with shaft and propeller. After making the changes, we will definitely use smb.



Unfortunately we had to use hydrazine. But this time we used much less. We dissolved one liter of hydrazine in one liter of distilled water. 

First, we added 500 cc to the solution and mixed it well. After a few minutes, we added another 500 cc and mixed well. We took a sample from the solution and performed a stannous test. The sample became completely dark. Then we added another 400 cc and mixed, even moving the settled gold particles. After 15 minutes and the particles settle. We tested the solution again, this time it darkened less but it was positive again. The color of the solution had changed from golden green to blue-green, but we were not sure. We added some precipitate again, it did not react when added, but reacted by stirring a small amount. We did the stannous test again, it was as dark as the previous test but like a semi-dark cloud, not black and purple. 



(We have doubts about the diagnosis of Stanus chloride test. Because the sample is blue and green. When we add a drop of Stanus chloride, a semi-dark cloud forms after a few seconds, but the blue color is still visible)



Add a little flocculant, mix well and leave for 30 minutes.



*Gold Filtering : *



At this point we did not use incomplete filters. We applied the *italimpianti* filter according to the photo. We used two paper filters and closed the filter with a rubber band around it. 

First we drained the salt solution of the base metals. When the gold sponge appeared, we started rinsing with hot pressed water in the tank. The gold sponge was drained slowly and hot water was passed over the gold several times. We kept the diaphragm pump on for about 30 minutes. The gold sponge dried a bit. (According to photo)



*XRF Pure Gold:*



We took some samples of gold sponge to test with Xrf . 

The result of the analysis:

Au:998.8

Pt:1.1

Ag:0.0

Cu:0.0

(We did not have platinum in the initial feed analysis.)



*Drying and melting:*



This time we dried the gold sponge with tow induction furnace. Fill the tow graphite crucible , after drying, turn off the furnace, add again, turn on the furnace, dry , and so on.

We did not add any flux.



One of the crucible was new. Another used.

We performed several XRF tests after melting.



1) XRF sample of new crucible:

Au:999.4

Ag:0.6



2)XRF sample of used crucible: 

Au:999.3

Ag:0.4

Cu:0.1

Fe:0.23



3) When I focused with XRF on the surface contaminated areas of the molten sample:

Au:968

*Fe:29.6 !!!!!!*

Cr: 1.9

W:4.9

Ru: 0.3

Zn:0.4



The discovery of iron surprised me. We did not dry the sponge with a steel container. Pure gold contact before melting was only with a steel spoon to fill the crucible. 

Is iron used in the production of graphite crucible?



We melted the gold again with some silver, to the 999 carat. A very small amount of impurity was observed on the molten surface during melting. It was shiny but not perfect. When draining the melt, add as much pinch of potassium nitrate and borax.





*Accounting:*



Total gold obtained without gold trapped in silver chloride and soluble cement:


*Finally we have 2122.65 gr (999)

We have undissolved 23.15 gr (755)

Gold recovered : 2850.67 gr (750)

Starting weight : 2859.8 gr (750)

Gold Not obtained: 9.13*

*Yield without AgCl and cementation:99.68*



*Cementation:*

We are preparing the second and third tanks for solution cementing with copper plates and air flow (according to 4metal recommendations). After finishing a few refining operations, we want to use them. 

Before the hydroxide tank, we had two cylindrical tanks and two waste water tanks. We want to make cement with copper plates in the cylindrical tanks. 

Also cement with atomize copper powder in tanks with mixers and air pipes. 

We are equipping them.

Obviously, the cement report is completed after a few operations to increase the solution.



Our solution has not yet reached the filter press stage, but we have adjusted the pressure of the hydraulic filter jack until no liquid escapes. 

We connected the filter press to the air for drying the hydroxides.

The waste water report will be completed.


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## 4metals (Jun 12, 2022)

Gold.refinery said:


> After an hour of reaction, we turned on the Tumbler rotating.


The tumbler should be running whenever the acid is reacting with metal in the tumbler. It is what provides the mechanical forces to break up encrusting silver chloride. If you ran the tumbler all through the reaction the undissolved alloy would be less. 

You also will have gold in the silver chlorides in addition to the chunks that you removed. Have you reduced the silver chlorides to metal and melted them?

The XRF result on the reduced Silver Chlorides that you melt into a bar will determine the actual quantity of gold that is missing. 

I am not really understanding what all of your numbers in parentheses mean



Gold.refinery said:


> *Finally we have 2122.65 gr (999)
> 
> We have undissolved 23.15 gr (755)
> 
> ...



I am traveling tomorrow morning but I will make you an excel spreadsheet to figure this stuff out in a manner that makes more sense. (at least to me!)


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## 4metals (Jun 12, 2022)

One question I forgot, and Orvi asked this but it was not answered. You refer to this material as karat and the XRF results do approximate 18 karat gold, but I am getting the distinct impression that this is not karat gold jewelry because of the cadmium. And the silver is very low for karat as well. Is there something here you are not telling us?


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## 4metals (Jun 12, 2022)

Gold.refinery said:


> Add a little flocculant, mix well and leave for 30 minutes.


You have never given us details about the flocculant you are using but you are now having iron issues in your fine gold. You do know there are iron based flocculants used for settling. After hearing some of the other advice the manufacturer of the equipment gave you, is it possible you are using an iron floc? 

The iron-based flocculants include ferric chloride, ferric sulfate, ferrous sulfate, and ferric chloride sulfate. 

What type of floc are you using?


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## Palladium (Jun 12, 2022)

When you took an XRF of the molten sample was that from the new crucible or the old one?


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## 4metals (Jun 12, 2022)

A few things about XRF.

An average energy dispersive benchtop XRF cannot determine impurities and distinguish readily between 99.5 and 99.95 purity.

So counting on your XRF to tell you it's .995 or .999 so you can add silver to cut it to .995 is not exactly a number I'd take to the bank.



Gold.refinery said:


> When I focused with XRF on the surface contaminated areas of the molten sample:
> 
> Au:968
> 
> ...


I have never, or don't know if anyone else has ever, used an XRF to shoot a molten pool of gold or any other molten metal for that matter. But it seems to me, that a device that measures secondary fluorescent energy that is emitted from an X-ray source just possibly gets it's numbers mixed up when it's looking at a sample that's glowing white and around 2000ºF above ambient temperature?

Is this like a thing????? Using XRF on molten metals in a crucible? How many of our members do this?


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## EMRE (Jun 12, 2022)

4metals said:


> A few things about XRF.
> 
> An average energy dispersive benchtop XRF cannot determine impurities and distinguish readily between 99.5 and 99.95 purity.
> 
> ...


Please no one should even think about doing that!!!! XRF needs to be less than 1 inch away from the (solid) object you are trying to measure.. Heat would burn the device...
I think he meant "Poured bar"


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## geedigity (Jun 12, 2022)

EMRE said:


> Please no one should even think about doing that!!!!


I absolutely concur with this. Damage to the unit will more than likely occur. It could even damage the shutter and lead to leakage of radiation (for XRF's containing a source).


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## Geo (Jun 12, 2022)

Have you tried magnesium sulfate as a flocculent?


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## Gold.refinery (Jun 13, 2022)

4metals said:


> You also will have gold in the silver chlorides in addition to the chunks that you removed. Have you reduced the silver chlorides to metal and melted them?


No,We have not yet converted silver chloride to metal.



4metals said:


> I am not really understanding what all of your numbers in parentheses mean


*Finally we have 68.18 ounce

We have undissolved 0.56 ounce

Gold recovered : 68.74 ounce

Starting weight : 68.96 ounce

Gold Not obtained: 0.22 ounce*

*Yield without AgCl and cementation:99.68%*


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## Gold.refinery (Jun 13, 2022)

4metals said:


> One question I forgot, and Orvi asked this but it was not answered. You refer to this material as karat and the XRF results do approximate 18 karat gold, but I am getting the distinct impression that this is not karat gold jewelry because of the cadmium. And the silver is very low for karat as well. Is there something here you are not telling us?


Gold scrap comes from a place that does not make 750 gold with standard ingots. 
Instead, they make 750-carat gold by *melting the previous scrap*. In scrap, cadmium is used to weld gold pieces. They also use less silver because of the price


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## Gold.refinery (Jun 13, 2022)

4metals said:


> You have never given us details about the flocculant you are using but you are now having iron issues in your fine gold. You do know there are iron based flocculants used for settling. After hearing some of the other advice the manufacturer of the equipment gave you, is it possible you are using an iron floc?
> 
> The iron-based flocculants include ferric chloride, ferric sulfate, ferrous sulfate, and ferric chloride sulfate.
> 
> What type of floc are you using?


Unfortunately!!! the manufacturer does not respond. I asked him three times. 
Now I have a sample of white powder not dissolved in water. I can test that white powder. Just remember to mention it is used in diapers. Maybe Sodium polyacrylate.!!!


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## orvi (Jun 13, 2022)

Gold.refinery said:


> We performed a new refining operation and applied some of the recommendations mentioned in this forum.
> 
> Obviously we could not implement all the recommendations due to device problems (until they are fixed soon)
> 
> ...



Thanks for the report of your operation. Few things I will point out:

1. Melting loss occur, and it is due to oxidation of some base metals in the melt - likewise that unfortunate cadmium. Use a good ventilation and respirator when melting this feed. *Cadmium will burn in the air*, even in melts like this.* It produce brown or brownish "smoke" or webs. Very toxic stuff.*

2. There will be some issues regarding your hydrazine precipitation of gold. I understand that it could be hard to see the difference between the "precipitates and colours" when not trained. But *gold in solution is black or violet* coloured. Only. You also have copper in solution - so *SnCl2 can also reduce Cu2+ into Cu+ and create complex compounds of copper which are dark coloured, but not black or violet*. Rather brownish colour. 

Eventually, if you will do the test on white plastic spoon with drop of gold solution (with copper) and SnCl2, you will see that the brownish colour will eventually go to colourless, as all copper will be reduced.

*You need to get completely familiar with SnCl2 test. You can also prepare training samples your own* - like take one grain of gold and 10 grains of copper, dissolve in AR and test. Observe. Then dilute. Test again. Then drop that little ammount of gold, do the test again. Observe. Etc 

I suspect the hydrazine could be lower percentage, or just it act in different way as precipitant, that I do not know. I will say it must be clearly evident when hydrazine is reducing gold - as it evolve N2 gas. Does the solution produce bubbles also after the last addition of hydrazine ? 

3. Flocculent, as 4metals pointed out, could be iron based. Not a big issue, since you will be melting gold anyway and it will slag out. There are plenty of flocculents in the market, like aluminium or organic-based ones, which does not harm your gold purity. But that is true also with iron.

4. I am curious how much precipitate you get after copper cementation. If some values made it past hydrazine precipitation, it would be clear how much. But majority of your gold would be locked in AgCl filtered precipitate - that is my bet. Try to pick a sample of AgCl and dissolve it in ammonia (just a gram or so). If there is locked gold, it would be very evident, since it won´t dissolve.

I think you make a steady progress. Accounting to the gold locked in AgCl, also some retrieved in cementation, that 9g loss will shrink  much better than in the beginning. We will steadily get it where it should end.


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## orvi (Jun 13, 2022)

Gold.refinery said:


> Gold scrap comes from a place that does not make 750 gold with standard ingots.
> Instead, they make 750-carat gold by *melting the previous scrap*. In scrap, cadmium is used to weld gold pieces. They also use less silver because of the price


Ah, now I see. I thought cadmium is excluded from all gold welding alloys... And yeah, it is cheaper than silver  and lower the melting point of alloy. So now I get it. But I am just curious where they could find so much 18K jewellery. I doubt that in EU, there is that much 18K circulating.


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## Gold.refinery (Jun 13, 2022)

4metals said:


> I have never, or don't know if anyone else has ever, used an XRF to shoot a molten pool of gold or any other molten metal for that matter. But it seems to me, that a device that measures secondary fluorescent energy that is emitted from an X-ray source just possibly gets it's numbers mixed up when it's looking at a sample that's glowing white and around 2000ºF above ambient temperature?
> 
> Is this like a thing????? Using XRF on molten metals in a crucible? How many of our members do this?


Testing the melt sample ??? !!!
Maybe it's misunderstood, I never thought about it at all. 
I meant testing the contaminated particles that stuck to the sample.(To detect the contaminating element)


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## Gold.refinery (Jun 13, 2022)

orvi said:


> *You need to get completely familiar with SnCl2 test. You can also prepare training samples your own* - like take one grain of gold and 10 grains of copper, dissolve in AR and test. Observe. Then dilute. Test again. Then drop that little ammount of gold, do the test again. Observe. Etc


Very useful , good idea


orvi said:


> Does the solution produce bubbles also after the last addition of hydrazine ?


In the last step of adding, we did not have bubbles. When we did sttiring, we had a little bit.


orvi said:


> There are plenty of flocculents in the market, like aluminium or organic-based ones, which does not harm your gold purity


Please tell me the exact brand name or Chemical name .
I'm not sure about the manufacturer and the his materials offered.


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## orvi (Jun 13, 2022)

Gold.refinery said:


> Very useful , good idea
> 
> In the last step of adding, we did not have bubbles. When we did sttiring, we had a little bit.
> 
> ...


I dont know how quick hydrazine is in precipitating gold - I just heard that it is fairly good precipitant for gold from more experienced refiners. So I trust them in this way. But it is possible that only the establishing the equilibrium takes more time. But that shouldn´t be an issue - since you left gold to settle for enough time.

To the flocculent, we used simple pool stuff - aluminium sulfate, or magnesium sulfate. But we hardly need any in refining, so my experience with exact brands and compositions isn´t the best.


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## Palladium (Jun 13, 2022)

O.K. I'm getting a little confused here. Is he using a floc in two different places? One for settling after precipitation and another for waste treatment. I've experimented with Gelatin for silver refining after precipitation, but i've also used _Sodium polyacrylate for the waste stream. Two totally different processes. And how much of this are you using at a time?_


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## 4metals (Jun 13, 2022)

I have likely dropped a ton of gold out of solution in my life. It’s heavy stuff. It tends to settle without help. Skip the floc with the gold.


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## EMRE (Jun 13, 2022)

Gold.refinery said:


> Very useful , good idea
> 
> In the last step of adding, we did not have bubbles. When we did sttiring, we had a little bit.
> 
> ...


you need to make samples like these for all metals. I did mine few years back for Pt and Pd because I wanted to see how much PGMS left in the solution and if it is worth going after or not. I suggest you make them for gold to start with. digest a know amount, take a sample, dilute it and take more samples. you can guess pretty good how much metal is in the solution left..


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## 4metals (Jun 13, 2022)

Gold Refinery,
Attached is a spreadsheet for you to fill out.
some of the numbers you have posted make no sense such as 


Gold.refinery said:


> Gold recovered : 68.74 ounce
> 
> Starting weight : 68.96 ounce


you only lost .22 ounces in processing?

fill in the yellow boxes (everything else is protected so you cannot accidentally change formulas)

*line 2. *starting weight for refining. this is the weight of scrap you melted and shotted and dried 
*line 4 *this is the assay of the gold, you have said .750 and .7554. it is one or the other. 
*line 6* weight of all of the refined gold melted
*line 8 *weight of the undissolved metal caught and separated from the Silver Chloride (it is best if you melt this into a button. Do you have a torch?)
*line 10*. the XRF reading of the undissolved button you just made
*line 12* the program calculates this
*line 14* the weight of the silver chlorides reduced and melted into a bar
*line 16* the XRF result for gold in the silver bar
*line 18* the program calculates this
*line 20* this is the weight of the gold you refined and melted plus the fine gold in the undissolved gold beads plus the gold in the reduced Silver Chloride bar you melted (summed up by the program)

cell G4 is the ounces expected from the start weight times the assay result.

with all of these numbers together the sheet will do the math and we will be talking about the same thing (we can hope!)

this program uses 31.1034 grams per troy ounce in the calculations

I think part of what is going on here is a language thing. Let's get the numbers straight first then we will know the losses you speak of without confusion.


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## EMRE (Jun 13, 2022)

4metals said:


> Gold Refinery,
> Attached is a spreadsheet for you to fill out.
> some of the numbers you have posted make no sense such as
> 
> ...


4metals,
I should mention that the assay of the insolubles should be slightly more than the beginning feed stock assay. in 14k lots, if the undissolved pieces are very small we see around 68%. if the pieces are large and intact it it would be close to the original feedstock assay. So technically the accountability of the sheet must be slightly better than 99.75..


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## 4metals (Jun 13, 2022)

Gold.refinery said:


> Instead, they make 750-carat gold by *melting the previous scrap*. In scrap, cadmium is used to weld gold pieces. They also use less silver because of the price


Here in the US cadmium is a metal we try to avoid. If you have cadmium in a lot you ship to a major refiner anything over 0.01% will cost you extra and over 1% they won’t accept it. 

For the safety of your employees melting scrap with cadmium as high as you see it on the XRF you should have a good exhaust over your melt furnace and for the environment you will be best served having a bag house to collect those webs of Cadmium that come off the melt. 

Cadmium is nasty. Dare I ask if you have good melt exhaust?


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## 4metals (Jun 13, 2022)

EMRE said:


> I should mention that the assay of the insolubles should be slightly more than the beginning feed stock assay. in 14k lots, if the undissolved pieces are very small we see around 68%. if the pieces are large and intact it it would be close to the original feedstock assay. So technically the accountability of the sheet must be slightly better than 99.75..


This is true. The numbers I put in the sheet were just to check the math. And the reason I made the sheet was to be sure we aren’t chasing phantom ounces. 

As you know Emre the base metals leach out before the precious in karat so any undissolved chunks do increase in assay. That is why he would be best served melting the beads together into a nice button for the XRF.


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## EMRE (Jun 13, 2022)

4metals said:


> Here in the US cadmium is a metal we try to avoid. If you have cadmium in a lot you ship to a major refiner anything over 0.01% will cost you extra and over 1% they won’t accept it.
> 
> For the safety of your employees melting scrap with cadmium as high as you see it on the XRF you should have a good exhaust over your melt furnace and for the environment you will be best served having a bag house to collect those webs of Cadmium that come off the melt.
> 
> Cadmium is nasty. Dare I ask if you have good melt exhaust?


we purchased some silver electrical contacts with 80% ag 5% Cd in it. when we melted it smoked that yellow poisonous gas soo much we almost had to evacuate. I dont buy anything that had Cd in it.. I am very surprised UK allows Cd in jewelery solder...


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## EMRE (Jun 13, 2022)

4metals said:


> Here in the US cadmium is a metal we try to avoid. If you have cadmium in a lot you ship to a major refiner anything over 0.01% will cost you extra and over 1% they won’t accept it.
> 
> For the safety of your employees melting scrap with cadmium as high as you see it on the XRF you should have a good exhaust over your melt furnace and for the environment you will be best served having a bag house to collect those webs of Cadmium that come off the melt.
> 
> Cadmium is nasty. Dare I ask if you have good melt exhaust?


Even if he did not have it before, I am sure he has it now with that nasty smoke..)))))))


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## 4metals (Jun 13, 2022)

EMRE said:


> I am very surprised UK allows Cd in jewelery solder...


I would bet it doesn’t. Nickvc would know best about this. As may Orvi.


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## EMRE (Jun 13, 2022)

4metals said:


> I would bet it doesn’t. Nickvc would know best about this. As may Orvi.


i have been reading this whole thing for two days now. It still seems a bit off. I am not sure why he even bothered with this? will he have enough incoming metal? he is not LBMA so it is not easy to sell it public, he may still end up selling to a refinery..


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## Palladium (Jun 13, 2022)

Yep! I had to put a copy of that spread sheet in my library. Thanks 4metals!


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## Yggdrasil (Jun 13, 2022)

EMRE said:


> i have been reading this whole thing for two days now. It still seems a bit off. I am not sure why he even bothered with this? will he have enough incoming metal? he is not LBMA so it is not easy to sell it public, he may still end up selling to a refinery..


I do not think he is UK. He said EU without specifying more, so that may be many places.


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## EMRE (Jun 13, 2022)

Yggdrasil said:


> I do not think he is UK. He said EU without specifying more, so that may be many places.


we should ask him where is he setting up this shop..


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## 4metals (Jun 13, 2022)

Gold Refinery,
I was looking at the photo and the movie you posted of the gold you dried in the filter and I realized that isn’t the filter you posted to start. The 3 are below. The movie looks to me like a vintage Italimpianti filter. 


The video you sent won’t load from my phone.


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## orvi (Jun 14, 2022)

As of UK, I have no idea if Cd is still allowed in jewellery, but I strongly doubt it. Here, it is present only in vintage scrap, and as far as I know, no jeweller nerby use cadmium solder for jewellery - either silver or gold.

And 4metals is right, for that ammount of Cd in the feed, there would be charges in established bigger refineries - so, that is maybe the reason why Gold.refinery is where he is, and doing what he is doing  
With ammounts he is processing, there is significant interest to do it "on your own", not to pay 1-2% + to the established refiner just for Cd content.


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## Gold.refinery (Jun 14, 2022)

4metals said:


> Attached is a spreadsheet for you to fill out.
> some of the numbers you have posted make no sense such as


Our calculations are posted in the photo. There are several difference.

We lost 2.17 grams in melting and flaking.
In fact, we did not get _*9.32 grams*_. But by calculating the Excel file 7.17 gr.

In addition, *we have not yet done copper cementation and also we have not done the recovery of silver chlorides.*


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## Palladium (Jun 14, 2022)

This is driving me nuts! I ran the numbers in the beginning of this thread. Maybe somebody else will chime in but are we really doing all this to find $422 out of $125,000? If this is what makes or breaks a multi-million dollar operation then i wouldn't even have started in this business. I understand squeezing a pig til it squeals.... I really do, but this is well within reason for accountability to the customer. The refinery will recover those values later own for it's own benefit. I have to ask, what kind of accountability are you giving to the customer? Are they buying this straight out from the customers? Are they charging a toll? There are so many other numbers missing from these equations.


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## orvi (Jun 14, 2022)

I see it that in chlorides, there will be some grams, after cementing we get maybe gram and that bring us practically to the error margin of the XRF...


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## Palladium (Jun 14, 2022)

orvi said:


> I see it that in chlorides, there will be some grams, after cementing we get maybe gram and that bring us practically to the error margin of the XRF...


From what i understand the whole show is run on XRF and not fire assay. I don't trust them guns that much myself. To me XRF is ballpark. Seen way to may lies from them guns. We haven't even talked about what package the gun is set up for or the calibration. This whole thing could be a wild goose chase of ghost numbers.


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## 4metals (Jun 14, 2022)

The time spent drying and re-weighing the shot before digestion is only done in production shops for one reason, to make sure all of the metal that left the office went through the melt and shot process and went into the reactor was not missing any metal. In other words to prevent, or guard against, employee theft. Most shops with decent security skip the step entirely. 


Gold.refinery said:


> We lost 2.17 grams in melting and flaking.


This loss is not precious metal, it is typical for lower melting point metals like zinc and in your case cadmium to burn off in the melt process. Those metals are currently evenly dispersed in the atmosphere of whichever country in the EU you are working. 

But in your case, since we are looking for grams here, 2.17 x .7564 grams or 1.64 grams of gold was not lost. 

Unless you re analyze the shot after flaking and enter the start weight as the weight after sharing the cadmium with your neighborhood, times the new XRF result, you have not taken the fact that only non precious metals volatilize. That 2.17 grams should not enter the calculus. Just enter the start weight before making shot and your starting assay figure.


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## jphayesjr (Aug 22, 2022)

4metals said:


> This is one of the smaller tumbler plants I have ever been involved with. This one has a capacity of about 6kg of karat scrap.
> 
> The reason I am showing these is because they all operate on the same principle as the plant we are discussing here, albeit from a different manufacturer. By seeing different systems we can gain a broader perspective.
> 
> ...


Ingenious technology. Recent news may describe a new technology that may simplify processes for us...https://newatlas.com/technology/graphene-recovers-gold-waste-electronics/?utm_source=New+Atlas+Subscribers&utm_campaign=0408f18f6f-EMAIL_CAMPAIGN_2022_08_22_01_48&utm_medium=email&utm_term=0_65b67362bd-0408f18f6f-91743941


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## PREMUG (Aug 25, 2022)

i have the same issue in commercial refining. For eg. We get individual dore gold bar lots .We accumulate and say we put in refining say 35,500gms we take dip sample for the same .This done in tandem by taking a dip sample for the individual scrap bars. So assaying is done on the general lot just before refining and individual scrap bars .After refining we separate the silver and get the unreacted popcorns. But nowadays even after taking out powder from the left over solution after precipitation. We still encounter losses to the tune of more than 0.5/kg of popcorn .we can lose more than say 17 Gms in this case. Can anyone put light on this phenomenon.?


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## Yggdrasil (Aug 25, 2022)

PREMUG said:


> i have the same issue in commercial refining. For eg. We get individual dore gold bar lots .We accumulate and say we put in refining say 35,500gms we take dip sample for the same .This done in tandem by taking a dip sample for the individual scrap bars. So assaying is done on the general lot just before refining and individual scrap bars .After refining we separate the silver and get the unreacted popcorns. But nowadays even after taking out powder from the left over solution after precipitation. We still encounter losses to the tune of more than 0.5/kg of popcorn .we can lose more than say 17 Gms in this case. Can anyone put light on this phenomenon.?


Not very easy to say as you have not said anything about the actual process equipment and so on.
As you have seen in this thread minor changes to the equipment setup or flow can result in increased or decreased loss.
And another thing is that some may not be actual loss as it can be reclaimed later.
Have you read this whole thread in detail?


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## 4metals (Aug 25, 2022)

Are you saying from a lot of 35,500 grams you have 500 grams of undissolved material? Or is that an accumulation of the insolubles from multiple lots? As Yggdrasil said, what type of equipment are you digesting in? 

Your issue is undoubtedly Silver Chloride but from your preliminary numbers your recovery is very good. 

There is much to talk about, such as assaying and spreads in your results and starting Silver content in the dorè. Too much for typing with my thumbs on a phone. 

Answer my basic questions and I will follow up in detail.


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## micklomenr (Sep 19, 2022)

Thanks for this interesting information!


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