Problem dropping gold using SMB in black solution

[deralm]

This is my second attempt at refining gold. The first attempt was a small amount as a test. Everything went fine. On this second attempt, I used a larger amount of gold. I used 10K and 14K jewelry. I'm using SMB to drop the gold and some gold is coming out but a lot of other metals or salts are also coming out, and the solution is very black.

I used AR to dissolve all the gold. This resulted in a dark black green solution. I let this sit overnight, and then filtered it in the morning. I used SMB to drop the gold but I believe only a little came out and there is a lot of white powdery stuff in the bottom as well. I believe there might be a lot of copper in the solution which could be causing a problem.

I've researched this all over the internet and this forum and seem to cannot find a solution. Any help would be greatly appreciated.

Thanks in advance.

 

[NobleMetalWorks]

What type of material did you digest?

The white powdery stuff might be too much SMB, or it could also be something like Tin Oxide.

Pictures and more information would be helpful.

You are probably correct about there being copper. If you digest in Nitric Acid first next time, you can dissolve the copper, or if you don't mind dissolving the copper slowly you can soak the material in hot HCl which should dissolve copper. The copper however shouldn't be causing you a problem with precipitating gold.

Did you expand your solution?

Did you test for gold in solution?

You can test the white powder by attempting to dissolve it in HCl, if it doesn't try a little Nitric Acid, if that doesn't dissolve the white powder, you probably have some type of insoluble material. It only takes a very small amount to test, I am talking drops. You can also test in AR, if it still doesn't dissolve you are in luck, you can wash and filter it really good without worrying about it contaminating your solution, just make sure you wash it really well.

Scott

 

[maynman1751]

You really shouldn't be dissolving karat gold in AR. You're dissolving all of the base metals with your gold. Not a good idea. Look up inquarting in the forum search. It will show you the proper way of refining karat gold.

 

[deralm]

SBrown - I will do like you said, and see if the white powder will dissolve in any of the acids. I will also try to post some pictures. Thank you for the advice.

maynman1751 - I will look into inquarting. Thank you for the suggestion.

 

[NobleMetalWorks]

Not sure how I missed the bit about it being Karat jewelry...

The material might be silver, it's probably silver in fact. If you try to dissolve silver in Aqua Regia, you end up with silver chloride.

There is probably a lot of other types of base metals, there could be tin, zinc, nickel and copper, and who knows maybe more.

Karat jewelry, depending on who alloyed it, can have almost anything in it. Get an assay done for all metals on a new piece of Chinese jewelry and you will see my point. Many of the refineries so far as I understand, in China, will reduce the Karat from 14k to 10k by throwing in whatever metals they have excess of. If you compare 10k Chinese made jewelry, one manufacturer against another, you will see a real color variance.

Also remember you might have Pd and even Rhodium from Rhodium plating of white gold.

Scott

 

[zzz]

The solution was hot(or semihot) or cold when you added smb?
if was hot, 100% sure that is silver chloride...if not, is someother thing

 

[Labman]

I don't like to use SMB (Difference me from the others on the forum) Many times has the mass spectrometer identified the white precipitate as 90% gold and 10% nickel when I have gotten a white powder from using SMB. It's better to inquart with copper and remove the base metals with nitric acid prior to using aqua regia. This way your precipitate will be dark brown and the melted button yellow instead of white.