# is it necessary to dilute AR before precipitation



## diverwild (Apr 30, 2017)

and what if I didnt dilute


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## 4metals (Apr 30, 2017)

It all depends on how much metal you have in solution. If you cleaned up the material you are refining with a leaching step and most of what you have in solution is gold, then it is not necessary, however if there was excess nitric in solution then it becomes advantageous to dilute it. We know little to nothing about what you are digesting or trying to accomplish so it is difficult to give a specific answer. 

More detail from you will help you get better advice.


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## FrugalRefiner (Apr 30, 2017)

It also depends on whether there was silver in your feed material. A concentrated AR solution will hold a bit of silver in the solution, which will contaminate your gold. Diluting the AR causes the silver to precipitate before you filter and drop the gold.

Dave


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## diverwild (Apr 30, 2017)

I work on refining jewelry polishing bags 18 k gold 
if dilution is not that necessary I prefer to precipitate without excess solution 
I denox that free nitric 
my steps are roasting the material completely 
apply a magnet to remove vibrator stainless steel balls 
crushing the material to fine particles 
then I put it in aqua regia without the first hcl wash


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## geedigity (Apr 30, 2017)

Unless you know for sure that your 18k dust and fines in the sweeps contains no silver, then do as Frugalrefiner suggested and dilute. I was amazed at how much silver chloride can be present in hot, concentrated AR resulting from processing karat scrap. Without dilution, it would be hard to know, that is until you begin washes with ammonia.


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## Nuwaysolutions (May 2, 2017)

One goal for precipitating gold is to get rid of the nitric acid in the AR. Boil down and refill with water several times should do the trick. 


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## anachronism (May 2, 2017)

Nuwaysolutions said:


> One goal for precipitating gold is to get rid of the nitric acid in the AR. Boil down and refill with water several times should do the trick.
> 
> 
> Sent from my iPhone using Tapatalk



There are many far more effective ways of getting rid of Nitric than that I promise.


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## g_axelsson (May 2, 2017)

You beat me to it Jon, http://goldrefiningwiki.com/mediawiki/index.php/Denoxing

Göran


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## diverwild (May 2, 2017)

the point of the question is to know the benefit of dilution، and if there is any negative effects if gold precipitated without it
and if distilled water may add a benefit


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## Topher_osAUrus (May 2, 2017)

diverwild said:


> the point of the question is to know the benefit of dilution، and if there is any negative effects if gold precipitated without it
> and if distilled water may add a benefit



They already answered that a couple posts up. But...

If your material has silver, it benefits you to dilute it so the (usually) insoluble silver chloride will precipitate out of the now weaker acid solution.

It also helps if you were just a little bit heavy handed with the nitric additions, if you used WAY too much nitric, you need other methods of denoxx, I for one would not go with water additions if evaporating, but instead small HCl additions. Also make sure you have a little sulfuric acid in the mix if you do choose the evaporation technique for removing your excess nitric.

It also helps if you use SMB for your precipitant by keeping the SO2 gas in the solution to reduce the gold.

You CAN dilute the AR solution too much though, so 3-4x volume should be more than sufficient.

Distilled water, tap water, makes no difference in this case. Ice would probably be your best bet, honestly. But, it seems as if there is a lot of stuff you should read up on to know when and why to use the ice.


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## anachronism (May 2, 2017)

Guys, he's asking about making less waste liquid. Depending how much he is doing, it's entirely possible that he would be better off not diluting the initial AR prior to drop. 

Diver are you doing a lot of this gold or just very small quantities, can you let us know how much please?


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## diverwild (May 2, 2017)

anachronism said:


> Guys, he's asking about making less waste liquid. Depending how much he is doing, it's entirely possible that he would be better off not diluting the initial AR prior to drop.
> 
> Diver are you doing a lot of this gold or just very small quantities, can you let us know how much please?



you got the point thank you
my refinings range from 110 to 170 g 18k gold in each process


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## anachronism (May 2, 2017)

Thanks.

Do you do this amount in one or more AR solutions and how much volume of raw solution would you use for each?


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## diverwild (May 2, 2017)

anachronism said:


> Thanks.
> 
> Do you do this amount in one or more AR solutions and how much volume of raw solution would you use for each?



One AR solution which I think weighs approximately 5 liters liters 
concentrated HCL and nitric I thought this is important so all gold become soluble untill yesterday I read a fourm in which Harold said he could use one liter for nearly 500g of dissolved gold in it and he had to use ice to let all gold precipitated so tomorrow I plan on using one liter of AR for each process 

if dilution has no positive effect on the process lets say it could make gold precipitate or settle faster or any other good benefit why would someone do it


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## diverwild (May 2, 2017)

I forgot to mention my AR is full of white ash and silver chloride which need time to settle for me to decant does dilution make it settle faster


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## anachronism (May 2, 2017)

You can process in less liquid to start with as you rightly pointed out. 5 litres is too much, so yes you can take that down. Experiment with 1 litre instead of 5 litres and try that. If that works then go smaller. 

Diluting 1 litre produces less waste than diluting 5 litres but that's just mathematics so I agree that reducing your liquid amount at outset is your first step. If you were to denox your solution completely, cool it, and once settled filter it to crystal clear then you will have very little silver left in the solution. Probably little enough to allow you to clean residual amounts of silver out of the precipitated gold powder using an HCl wash or two. 

Good filtration is the key to this. 

I would recommend experimenting as you will soon see silver chloride on your gold powder as a white fluffiness. My advice would be to try what I have suggested above. If you find you have small quantities of silver left, then there is nothing to stop you redissolving the gold in a very small amount of liquid- and then following the "dilute by three times" approach because diluting a couple of hundred cubic centimetres will produce way less waste again.

Jon


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## diverwild (May 2, 2017)

thank you for your time


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## 4metals (May 2, 2017)

The problem with processing burnt sweeps in aqua regia is the amount of gold that is retained in the ash sludge from poor rinsing. To get the most out of the sweeps you need to rinse them well. Fortunately the rinse waters is very dilute acid and it contains your gold that did not filter out of your digestion. You can either set up a glass still and boil off the water to make a concentrate of the aqua regia that the sweeps contained. If it's sunny and dry where you are consider a solar still for your dilute wastewater. 

It is good practice to place a few drops of stannous chloride on your filtered ash. If the acid still contains gold it will indicate that to you. 

I have 2 clients that have a large centrifuge made just to spin solutions down to avoid time consuming filtrations on sweeps. The problem is they have to add water and mix the sludge at least 3 times to get all of the retained acid from the sludge. So the volume creeps up from adding water before filtering or on the other end when the sludges retain too much value. 

Why do you start in Aqua regia? If you did a first leach in nitric and distilled water you could also recover the silver. Once the silver has been through aqua regia it is much more difficult to get out the silver.


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## diverwild (May 3, 2017)

4metals said:


> Why do you start in Aqua regia? If you did a first leach in nitric and distilled water you could also recover the silver. Once the silver has been through aqua regia it is much more difficult to get out the silver.



Do you think nitric could attack 18K alloy dust?


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## 4metals (May 3, 2017)

Dust, likely it may because the particles are small, but you are looking to leach out the silver not dissolve the gold. What percentage is the silver in the 18K alloy?


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## diverwild (May 3, 2017)

4metals said:


> Dust, likely it may because the particles are small, but you are looking to leach out the silver not dissolve the gold. What percentage is the silver in the 18K alloy?



0.16 each gram the alloy contains Cadmium too


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## snoman701 (May 3, 2017)

diverwild said:


> 4metals said:
> 
> 
> > Why do you start in Aqua regia? If you did a first leach in nitric and distilled water you could also recover the silver. Once the silver has been through aqua regia it is much more difficult to get out the silver.
> ...



The answer to the question is yes, nitric oxidizes the small particles and that is what you are seeing as an attack. 

It's the premise of touchstone testing.




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## snoman701 (May 3, 2017)

Is cadmium a normal alloy component with gold? 


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## 4metals (May 3, 2017)

When you burn the sweeps and crush them, any oversize that doesn't pass through a 40 mesh screen is usually metallic gold from filings. This material needs to be inquarted with silver and parted in nitric in order to recover the gold. 16% silver is too high to completely digest the gold in aqua regia without hanging up gold in the silver chlorides, so for the oversize, inquart. 

At 16% and the fine particle size you crush to, a nitric / distilled water leach should get a good percentage of the silver out. Filter out the insolubles and recover the silver from the acid. (Cementation or as a chloride, your choice)

You do not have to worry about any nitric that may remain in the solids because you are going to make aqua regia anyway, so another incineration isn't needed. Just add the hydrochloric acid and the nitric to dissolve the gold. Heat for the dissolve will help as well. When everything is reacted and filtered, I always like to take a small spoonful of the filtered and rinsed solids and add them to a small beaker of aqua regia, then test with stannous to see if any gold was dissolved. 

I never mix up aqua regia the same strength for sweeps as for karat scrap, I usually start at 8:1. By testing the processed solids in a small beaker if aqua regia you will learn what ratio of acid works best for your material.


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## diverwild (May 4, 2017)

snoman701 said:


> Is cadmium a normal alloy component with gold?
> 
> 
> Sent from my iPhone using Tapatalk


it comes from solder، when we polish a piece the buffing wheel hits places which has solder that ends up in the polishing bags that I need to refine


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## diverwild (May 4, 2017)

4metals said:


> When you burn the sweeps and crush them, any oversize that doesn't pass through a 40 mesh screen is usually metallic gold from filings. This material needs to be inquarted with silver and parted in nitric in order to recover the gold. 16% silver is too high to completely digest the gold in aqua regia without hanging up gold in the silver chlorides, so for the oversize, inquart.
> 
> At 16% and the fine particle size you crush to, a nitric / distilled water leach should get a good percentage of the silver out. Filter out the insolubles and recover the silver from the acid. (Cementation or as a chloride, your choice)
> 
> ...



I will try what you have suggested then I will reply، BTW there are no oversized pieces in the polishing bags، when I sieve the incinerated ashes I cant see any gold particles at all they are very very small and mixed with ash

since we opened this topic I have one concern which is iron or stainless steel I use a magnet after sieving، but lets say some amount of iron went to AR what problems could occure ?
because I dont make the first step washing with HCL I made it once and the solution took long time for me to settle and decant


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## diverwild (May 6, 2017)

4metals said:


> At 16% and the fine particle size you crush to, a nitric / distilled water leach should get a good percentage of the silver out. Filter out the insolubles and recover the silver from the acid. (Cementation or as a chloride, your choice) /quote]
> 
> I hoped what you suggested would work، but it did not، I boild my incinerated material for about half an hour with nitric، then decanted، nitric became green in color، then had my material in AR by adding HCL، 15 minutes later the solution was full of creamy silver chloride which resisted the initial nitric digestion،
> 
> ...


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## Topher_osAUrus (May 6, 2017)

What concentration of nitric did you use on your half hour nitric boil?
Did you test the green nitric leach with stannous or dmg to see if any palladium was in the solution?

If the solution got any sunlight, the black is probably silver chloride.


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## diverwild (May 6, 2017)

Topher_osAUrus said:


> What concentration of nitric did you use on your half hour nitric boil?
> Did you test the green nitric leach with stannous or dmg to see if any palladium was in the solution?
> 
> If the solution got any sunlight, the black is probably silver chloride.


68% concetrared 
No I did not our 18 karat does not have PMs other than gold and silver.


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## FrugalRefiner (May 6, 2017)

diverwild said:


> Topher_osAUrus said:
> 
> 
> > What concentration of nitric did you use on your half hour nitric boil?
> ...


Did you dilute that at all, or did you boil it at 68%?

Concentrated acid has little "room" left for metal ions. When we use nitric to leach silver, palladium, or base metals, we usually dilute concentrated nitric acid with an equal amount of distilled water. The silver (or palladium, copper, etc.) nitrate is soluble in the water used for dilution.

Dave


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## diverwild (May 6, 2017)

FrugalRefiner said:


> diverwild said:
> 
> 
> > Topher_osAUrus said:
> ...



after boiling a bit I added nearly 1 liter tap water


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## 4metals (May 8, 2017)

The reason you use distilled water and nitric is to allow the silver to leach out of the alloy. Granted at the ratio of gold to silver this may be difficult you did 2 things that did not help the situation. First you used full concentrated nitric acid and Dave explained the problem with that, and second you added tap water which provided a source of chlorine to form a film of silver chloride on the gold. 

Before you give up on leaching out the silver, try doing it properly by diluting the concentrated nitric with an equal volume of distilled water. 

At 18% silver you aren't getting all of the gold with aqua regia either so try to leach it properly so as to eliminate any possibility of premature chloride formation. Rinse it well with distilled water, and then try aqua regia. If you can successfully lower the silver content the gold dissolution will be more complete.


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## diverwild (May 9, 2017)

4metals said:


> First you used full concentrated nitric acid and Dave explained the problem with that, and second you added tap water which provided a source of chlorine to form a film of silver chloride on the gold.


I think this is where it went wrong، could chlorine along with nitric dissolved some of the gold?

next time I will try it with 50/50 distilled water، and reply 
thank you my friends.


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## upcyclist (May 9, 2017)

diverwild said:


> 4metals said:
> 
> 
> > First you used full concentrated nitric acid and Dave explained the problem with that, and second you added tap water which provided a source of chlorine to form a film of silver chloride on the gold.
> ...


The more likely scenario is that the chlorine in your tap water reacted with the silver nitrate to form silver chloride. The silver chloride crust then prevented the nitric from getting to the silver and the AR from getting to the gold.


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## anachronism (May 9, 2017)

Diver- you need to look at the chemistry of AR, because when you do and learn it you'll not be asking if some Chlorine in Nitric will dissolve gold. I mean that kindly- it's the basis of most of what is done with gold refining (apart from cyanide leaching) on this forum. 8) 

I'm not entirely sure what search term would be best could someone help me out? 

Jon


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## upcyclist (May 9, 2017)

anachronism said:


> I'm not entirely sure what search term would be best could someone help me out?


I'm thinking some Hoke reading is in order before he even attempts the forum searching.

Diverwild, check out Dave/FrugalRefiner's signature block--he posted the second reply to your OP. Click on one of the Hoke links and read up--then you'll have a much better knowledge base from which to start querying the forum and its members.


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## diverwild (May 9, 2017)

Your time in helping others is more precious than gold، spending few ounces(time) with us is much appreciated .


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## diverwild (May 9, 2017)

I thought chlorine = chloride، I am not a chemist but I like chemistry and enjoy reading about it، I read a lot in this fourm about chemistry، and you all know reading is the best way for a proper knowledge.


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## upcyclist (May 9, 2017)

diverwild said:


> I thought chlorine = chloride


You are absolutely right--but it didn't react with the nitric acid to act like an oxidant. AgNO3 + Cl- = AgCl + NO3-


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## diverwild (May 11, 2017)

anachronism said:


> Diver- you need to look at the chemistry of AR, because when you do and learn it you'll not be asking if some Chlorine in Nitric will dissolve gold. I mean that kindly- it's the basis of most of what is done with gold refining (apart from cyanide leaching) on this forum. 8)
> 
> I'm not entirely sure what search term would be best could someone help me out?
> 
> Jon



well my friend، I am realy surprised it actually had gold، 
yesterday a friend of mine gave me old japanese solder senju 1976، to prepare stannous chloride (which I never used before)، I made the test solution، and I had to test its efficiency، I had only that nitric solution which I used in the first wash، it gave light purple color، which made me skeptical، I evaporated the solution with maximum heat untill the solution became very green I put some HCL، let cool، filtered، SMB precipitation، I recovered 0.4 gram of gold، then the solution became pale blue، with stannous test it gave yellow color، I was very happy with this experiment  
but how nitric digested some gold along with tap water.


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## FrugalRefiner (May 11, 2017)

diverwild said:


> but how nitric digested some gold along with tap water.


Nitric acid plus the chlorine in your tap water creates AR and dissolves gold.

Dave


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## anachronism (May 11, 2017)

FrugalRefiner said:


> diverwild said:
> 
> 
> > but how nitric digested some gold along with tap water.
> ...



Hence my post about understanding the AR chemistry.


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## FrugalRefiner (May 11, 2017)

anachronism said:


> FrugalRefiner said:
> 
> 
> > diverwild said:
> ...


Yes, I know. I just tried to provide the explanation a little more directly.

Dave


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## anachronism (May 11, 2017)

Dave it wasn't directed at you, it was directed at the OP 8) He's obviously missing the correlation with this.


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## upcyclist (May 12, 2017)

A simple rule that will make your life easier: don't use tap water with any processes involving nitric acid as your only acid. The chlorine tends to either make AR or AgCl. Probably ditto for sulfuric. Use distilled water.

In the summer, water off my old dehumidifier coils is as effective as distilled water (as long as the tank is clean and mildew-free). It's essentially distillation without the heat, since it condenses the moisture in the air instead of heated water vapor from boiling.

In an informal lab, you can use tap water with HCl, but if you really want to run a tight ship, only use distilled water. That way you have more control over what chemicals are present in your work.


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