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.
consolidation of Loss Gold thread
- Thread starter 4metals
- Start date
Help Support Gold Refining Forum:
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.
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.
This will be useful as a picture speaks more than words.
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.
Gold.refinery
Well-known member
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?
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?
Gold.refinery
Well-known member
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 ?
You said with a mesh less than 2.5 microns.
Is this for both ?
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.
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.
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.
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.
Gold.refinery
Well-known member
Unfortunately I could not figure out your solution for the tank floor valve.
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.
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.
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.
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.
Gold.refinery
Well-known member
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.
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.
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!
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.
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.
Last edited:
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.
I bought some borosilicate glass tubing and added a 6 in piece inline past the reaction vessel so i can do just that.
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.
Last edited:
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
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.
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.
Last edited:
Gold.refinery
Well-known member
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.
Gold.refinery
Well-known member
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?
