What went wrong?

[naporex]

Hi
Lately I've made my another inquarting refining but this time something went not like it should. I'll start from beginning.
I've decided to refine some scrap gold I've buyed lately so I did my calculations for inquarting like wise books says -> 6K alloy.
Then a client came with a strange bottles of powder called "Stabil-B" (Stabil-B contains: 68% Ag, 27% Sn, 4% Cu, 1%Zn) and I thought: hmmm why not to melt it with gold scrap and refine gold and silver at one time? Like I thought I did it. I've melted all together BUT there was mnuch more of the Stabil that I needed to get 6K gold I think it went to 3K or less. Anyway I've melted it, poured and tried to rolled out for a thin sheet. When I tried to rolling te bar just crack out into pieces! like a piece of glass so I've stopped. I've put those pieces into a flask, puired some distilled water and started to adding HNO3. Everything went like usual until end of the process Ive addend another portion of acid (after few earlier of course) and then suddenly solution went from dark blue into totally balck. Ithought ok lets see what will happend because while boiling the No2 fumes still were going out. when they stops forming I've turned off heat, put the flask out of hot plate and waited to settle down but... it won't. The solution was still black, I mean not dar but totally black like an ink. After taht I tried to filter it but the solution that came from filter was also black so I thiught that I might dilute the gold too much in an alloy and maybe it's going thru filter, so I've just washed/decanted few times with distilled water ansd then proceeded to aqua regia step. All went ok until I sam win soution white sediment wich didn;t want to settle down I've tried to filter it but still it came by filter. Ok next step was SMB - added - powder shows up - settled down - decanted, washed, dried and melting... and I saw something strange. Gold melted but veery slowly coldificated lie a stannous for electronic use I think. After it cooled and solided out It was.. purple/pink coloured :roll: Today I took this alloy again with some more silver and scrap gold, melted, same process with HNO3 and... same situation solution came totally balck. What is wrong? how to extract gold from this. I really have no ide what to do. BTW when I diluted the solution with distilled water it came a violet colour maybe this will help to solve this problem. Thanks in advance.

 

[butcher]

naporex,

The added tin caused a big mess, which makes losing your gold easy, you have created a big problem that is not easy to get out of, or easy to get all of the gold back out of.

Hope you have not thrown any thing away saving any liquids or solids that were involved.
the tin in nitric makes a gelatinous gunky solution that can trap values, making filtering almost impossible.
The gold can colloid in a solution with tin, locking gold up in the solution, you cannot test for it, you cannot cement it out of solution, you cannot filter it out of solution.

If there are gold ions in solution you can test for them, (but not the colloidal gold) and you can cement the gold (ions) back out of the solutions.

You may just have to evaporate the solution to dry, and then start over dealing with the tin and base metals to get the gold back out of the mess, separating the tin and base metals from your gold.

 

[Palladium]

This is where a good pyroceram dish comes in handy. I've had to do what butcher is talking about. Evaporate to dry, incinerate, and then a hcl wash followed by ar. All right in the dish. Get rid of that tin! You're right, it looks like ink and will clog a filter up and yet some still seems to always magically appear on the other side of the filter.

 

[naporex]

Of course I didn't throw up anything, poured liquid yesterday to a can and what's left in a flask washed with some distiled water and left overnight. Today morning I saw black powder settled down in a flask. and solution was white clear. So You say to dry that powder then incinerate right? I have to get ceramic dish for this. One more question: If I did some water washing and powder settles down (correct me if I'm wrong) no gold was disolved since there was no HCL in use at this stage only HNO3?

 

[butcher]

Colloids are so small they will be invisible in a solution, they can sometimes be detected by the reflection of light, light shined through a solution and viewed from the side you may see the reflected light when colloids are present.

The violet color we see with gold solutions and our tin chloride solution (in testing for gold), this is a certain size gold colloids reflecting the light to give that purple color.

Colloids although extremely small can be different sizes and reflect light to give different colors.

A pure colloidal solution (silver for example) can be as clear as water, with no color, you cannot see the silver or see the billions of clusters colloidal silver metal in the solution.

You are correct gold will not dissolve in HNO3 alone, as long as there are no HCl or halide, or salt of these involved.


I would dry and give powders an good hot roasting in the incineration process, to oxidize any tin and other base meals, this also helps to burn off any oils or organics.

Then boil in HCl and taking up the solution with water, will help to improve these powders.

This process to deal with tin has been described and discussed many times on the forum, you should have no trouble finding these discussions on the forum to learn more of how the process works and its benefits.



Gold and chlorides together at around the temperatures of incineration, can dissolve gold in the fumes produced, and can carry some gold in the smoke, for this reason I try to convert any chloride metals involved to oxides or hydroxides with NaOH and wash out the salt water formed, before roasting,(if your powders do not have chlorides metal salts, you can skip this step).

 

[naporex]

Ok thank You butcher I will try to recover like You wrote. Thanks.