# Aqua Regia with Sodium Sulphide precipitation



## arsenic123 (Mar 31, 2014)

Hello guys today I processed gold dust about 5 kg and my process is as follows. I didn't had any issue but I just want to write my process down with photos and I want to know what could of have I done to make it more better. 

1st photo is the dust photo. I grind it well and made the powder. The steps are :
1) I burned the dust after grinding and the photo is attached here. next I dipped the dust in to HCl (32%) and stirred well. Then I started adding Nitric acid (72%) slowly slowly. The ratio of HCl and Nitric acid was 1:3. kept on stirring for 20 minutes and then stirred at regular interval like half an hour and kept the material in the bucket for 24 hours. 

2) Next day added little Urea too because there was excess nitric acid and kept on adding till there was no bubbling and reaction. Next day I washed the material nicely and the gold which was now in solution was precipitated by sodium sulphide. Kept on adding sodium sulphide till there was no precipitation. 

3) Next step was filtering. After filtering this was the result. (Please see photo 2) 

4) Now my final step i.e melting is still remaining but I just wanted to show you the progress. 

My question is can SMB be used as a precipitation in place of Sodium sulphide? Also HCL-CL would have given the same result or better result after seeing the pictures? What do you guys think??


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## goldsilverpro (Mar 31, 2014)

What was the source of the "gold dust"?

Where on earth did you get the idea of using sodium sulfide? SMB is selective for gold and would have been a much wiser choice. I may be wrong but, by the look of things, you have a mess.


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## arsenic123 (Mar 31, 2014)

goldsilverpro said:


> What was the source of the "gold dust"?
> 
> Where on earth did you get the idea of using sodium sulfide? SMB is selective for gold and would have been a much wiser choice. I may be wrong but, by the look of things, you have a mess.



Actually I had used sodium sulphide previously and I was able to recover 110 mg of gold per kg earlier. The source of the gold dust is still unknown because I had got it at a very cheap rate from my friend. According to me it was from a factory in which gold plating work is done. Attached here is a picture of sodium I used.

Also I think if I had used stannous chloride test after precipitation I might have got more gold in the solution which I had discarded. Thanks


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## Pantherlikher (Mar 31, 2014)

Sounds like you did the whole thing blindy as you probably added too much Nitric acid. You did not denox properly. Use something close but not right to precipitate. And you did no tests to see if and where ALL the gold is.

Bummer

B.S.
...Are those broken up potato chips?..


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## arsenic123 (Mar 31, 2014)

Pantherlikher said:


> Sounds like you did the whole thing blindy as you probably added too much Nitric acid. You did not denox properly. Use something close but not right to precipitate. And you did no tests to see if and where ALL the gold is.
> 
> Bummer
> 
> ...



Those are sodium sulphide not potato chips.. 

Actually I had done this process in past so it is not a blibd method and I also know people use oxalic acid as well to precipitate but that is very expensive and the place where I had done it didn't had smb so I actually didn't had any options.


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## joubjonn (Mar 31, 2014)

I wouldn't even use nitric for that. HCl / bleach would work well on dust. But 110mg per kilogram? Doesn't even sound worth it. Would be a huge mess and a bunch of chemical to get rid of.


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## arsenic123 (Mar 31, 2014)

joubjonn said:


> I wouldn't even use nitric for that. HCl / bleach would work well on dust. But 110mg per kilogram? Doesn't even sound worth it. Would be a huge mess and a bunch of chemical to get rid of.



In my country 110 mg is considered as the best dust for refining. It is considers as high yield material because high average dust is usually sold to big refiners and its very costly so small refiners use this lots. Infact we buy material which only have 70 mg per kg happily.


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## Juan Manuel Arcos Frank (Mar 31, 2014)

Arsenic123:

I agree with GSP...sodium sulphide is a very different material than SMB...sodium sulphide turns all soluble precious metal´s salts into sulphides...SMB reacts(in acidic media) to form SO2 which will reduce gold chloride and precipitates gold mud.Now,you have a mess to deal with...

My advice to you is following my silver sulphide method to obtain a metal alloy(Au,Ag,Cu and so for) and process the alloy by inquartation process to separate Au from Ag and base metals.

Keep it in mind...SMB is the selective precipitant for Au,sodium sulphide is the precipitant for almost all metals and if you want to precipitate a precious metal as its sulphide then you have to be completely sure that there is not any other metal in solution.

Hope it helps.

Kindest regards.

Manuel


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## joubjonn (Mar 31, 2014)

True. It would be amazing content for someone with a trommel running a few hundred yards of dirt. Probably better then anything we ever saw on the gold rush show on discovery. But for doing it chemically it just seems like it would be difficult. All that dust has surface area. I would think the AR would stick to that causing losses to be too great compared to content. If that makes sense. I don't know what your dust is like but if you could find a way to reduce the volume of the dust without loosing any gold like burning it that would probably help. It would depend on the particle size of the gold 

Maybe you could try to submerge it in water with a small amount of dish soap to take care of any surface floating. Shake this in a glass container and see if you get a pay streak at the bottom and scoop off the rest.


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## Geo (Mar 31, 2014)

Sodium sulfite will precipitate gold and sodium sulfide will make a mess. Check the name of the chemical used if you are in doubt. If you are sure that you used sodium sulfide, you have much more work to do to get the gold out.


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## goldsilverpro (Mar 31, 2014)

What country are you from?

How much total weight of this stuff do you have?

So, you might have a little over a gram of gold in that 10kg of material. Before, when you did the kilo, what process was used to get the 0.11g of gold out of the precipitated material (like the stuff in photo 2)?

At this point, your process looks like a big no-win proposition to me, no matter what country you live in. Very little gold (about $2/pound or $4.50/kg) for a lot of work and a lot of chemicals. However, it may be worth more. Before going any further, I would try to find out what it is really worth so you would have at least an idea what you are really looking for. The ground up material could be split down with a sample splitter or by "coning and quartering" (Google) and then a couple (at least) of separate samples could be taken and fire assayed. You may find that you are losing a lot of gold in your very questionable process or, you may find out it is not even worth doing, at least with the method you've chosen. 

I spent much of the 1st 10 years of my working life troubleshooting plating systems in 100's of gold plating facilities and I'm having trouble figuring out where in a plating shop that "dust" might be generated. About the only thing I can figure is that it's floor sweeps or evaporated water from mopping the floor around the gold tank.


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## arsenic123 (Mar 31, 2014)

Juan Manuel Arcos Frank said:


> Arsenic123:
> 
> 
> 
> ...



Oh Manuel you are so correct. Last time I had followed the similar process to obtain gold and silver. The process was to burn the sludge listed in photo number 2 usin borax and then melt the remaining powder in furnace. After that use a method to form a ring type or circle which contains all precious metals. Then the furnace guy takes metal out of that ring one by one.


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## arsenic123 (Mar 31, 2014)

goldsilverpro said:


> What country are you from?
> 
> How much total weight of this stuff do you have?
> 
> ...



I have around 100 kg of the material. The profit i am getting is around $5 per kg. I know its very less but I am not that rich so its actually worth doing it specially in India where there is so much competition for gold dust. I will definately do Google for the methods you have said and already started reading hoke's book and I have also ordered Steve CD set which will arrive this week hopefully. I hope all this will help me. Thank you so much for the inputs. Great place to learn with great people.


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## goldsilverpro (Mar 31, 2014)

> After that use a method to form a ring type or circle which contains all precious metals. Then the furnace guy takes metal out of that ring one by one.


I'm having trouble understanding what you mean by this.


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## arsenic123 (Mar 31, 2014)

goldsilverpro said:


> > After that use a method to form a ring type or circle which contains all precious metals. Then the furnace guy takes metal out of that ring one by one.
> 
> 
> I'm having trouble understanding what you mean by this.



I am not sure how to put it but the process after picture 2 is basically burn-melt-make alloy rock which contain gold, silver, copper, etc-take out metals one by one using the temperature needed for each alloys. Actually I dont do it the furnace guy do that so I dont know what does that method called. But I will tell you after melting the furnace guy takes cement, use lead and make a dish type of rock in very thick iron bucket and lastly he blows air and all. Its very complicated.


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## joubjonn (Mar 31, 2014)

I think he's talking about the lead button in fire assay. I think

So much chemicals for that. I just can't see the profit. Unless you get free chemicals and have a lot of time with it. And then convincing a buyer of your 1 gram button of 24kt gold. Reduce that material some how. Make life easier for you.


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## arsenic123 (Mar 31, 2014)

joubjonn said:


> I think he's talking about the lead button in fire assay. I think
> 
> So much chemicals for that. I just can't see the profit. Unless you get free chemicals and have a lot of time with it. And then convincing a buyer of your 1 gram button of 24kt gold. Reduce that material some how. Make life easier for you.



Oh great I guess that is what its called. Lead button in fire assay. Because he does use lead. Thanks 
Usually I get 1 gram in 10 kg. Profit is low, totally agree with you. The chemicals are actually free because I use chemicals stored in my boss's factory and he told me to use it for small lots if I have my own dust. He is a kind man.


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## goldsilverpro (Mar 31, 2014)

joubjonn said:


> I think he's talking about the lead button in fire assay. I think
> 
> So much chemicals for that. I just can't see the profit. Unless you get free chemicals and have a lot of time with it. And then convincing a buyer of your 1 gram button of 24kt gold. Reduce that material some how. Make life easier for you.


I agree with joubjonn. If you could reduce the amount of material somehow (gravity; flotation; incineration; etc.) before using the chemicals, it would sure be better. Do you know what form the gold is in in the original material? Gold metal? If it really is from a plating shop, it is more likely to be a dried gold salt, such as potassium gold cyanide. If that's the case, it may be only partially soluble in aqua regia, if at all.


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## Geo (Mar 31, 2014)

wouldn't adding zinc to the melt convert the cyanide salts back to elemental gold?


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## goldsilverpro (Mar 31, 2014)

Geo,

The gold compound in all modern acid gold plating baths is KAu(CN)2 and most operate at a pH of from about 4.3 - 6.0. If the pH is allowed to go below about 3.5, the canary yellow AuCN precipitates, which is insoluble in strong acids. For example, if HCl were the acid added, the reaction would be:
KAu(CN)2 + HCl = KCl + HCN(gas) + AuCN(solid)

The AuCN is soluble in only an alkaline cyanide solution or ammonia, as far as I know.

I can't see how zinc in a melt would do anything except alloy with what other metals are present.


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## Geo (Apr 1, 2014)

I dont know why I thought of that. Seems like I read something about thermal oxidizers or something like that. Metals that release oxygen when decomposed at high temperatures. It may not have even been zinc. I really need some kind of database where I can store and retrieve information when I need it. Well, one day we will all have something like that in our homes.


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## arsenic123 (Apr 1, 2014)

goldsilverpro said:


> joubjonn said:
> 
> 
> > I think he's talking about the lead button in fire assay. I think
> ...



yes I suppose gold is in dust form and the material is I think is dust or floor sweep. That is the reason the average is so low. As I said earlier that I am getting the material cheap and my friend is probably getting it for free so thats why he is not disclosing the source. Regarding the incineration I already burned it before processing with chemicals.


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## joubjonn (Apr 1, 2014)

I just can't imagine trying to process that much material for the amount in it

I get annoyed with 1 gram of gold in 100 grams of incinerated IC concentrate after removing the ash. I almost don't even want to deal with it sometimes.


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