AR - No drop - how to proceed

[limestonecowboy]

Done many sucessful AR treatments no problem, but this time no drop.

Ok, so I dissolved 20 grams of 9ct gold scrap in warm AR- all disolved quickly, with a nice yellow green colour as normal.

left to cool and then added urea as normal untill no fizzing then a couple of gr extra to be sure.

left for 4 hours then added SMB.

Only a tiny amount of gold dropped. Added more SMB, nothing, added a little extra water, still no further drop.

Stanous test shows a strong positive for more dissolved gold.



do I heat, simmer, evaporate or add zinc ?

Im not sure where I went wrong this time but obviously I did, may be a contaminate or something, but for now I just want to recover my gold, any suggestion (exept Hoke, which I have in my hand right now)

Just want opinions on how best to proceed to salvage my values,

Best wishes to all, thanks in advance,

Rich,

 

[Harold_V]

You might consider using copper instead of zinc, which will precipitate everything in solution. That way you will have recovered the values without recycling the base metals with the gold.

If you try the copper idea, some of the values will stick to the copper unless you have an excess of nitric. If so, a small amount added when the values have been cemented down (test with stannous chloride) should liberate anything that sticks to the copper. You likely already understand that the values will come down dark, likely not resembling gold.

Harold

 

[limestonecowboy]

Many thanks Harold, your advice is always appreciated.

After an unsucessful attempt with cementing down with copper (I dont know why this failed either) I decided to boil down and evaporate to solids.

I now have a pretty blue-green powder which I presume is a combination of my metals, my acids, my precipitant (smb) and urea.

The solids were actually a deep golden yellow colour right until the last moments of evaporation and then they turned greenish as they dried.

So now I need some help on the next step.

I have tried incineration with a small trial sample and can see some gold and copper melting up into beads, but lots of nasty residues and oxides, so can I rinse the powder in water to remove the solubles before re-treating with acids ?

Cheers Rich.

 

[lazersteve]

Rich,

Try washing the junk out of the sludge with HCl.

The precious metal should remain behind.

Gold will be elemental gold (dark powder) and silver will be silver chloride (purple gray powder).

Be sure to test the HCl for dissolved gold before proper disposal.

Steve

 

[Harold_V]

After an unsucessful attempt with cementing down with copper (I dont know why this failed either) I decided to boil down and evaporate to solids.

The reaction may not be instantaneous, and likely wouldn't be.

When I recovered silver from a nitrate solution that also carried platinum and palladium (you may recall that platinum will dissolve in nitric in the presence of silver), the silver came down instantly, while the other values came down only after the silver was completely cemented, and then slowly.

You can judge the reaction by inspecting the copper. It will have a dark deposit on the surface. If you don't get a reaction, the addition of a few drops of acid will generally encourage the process.

When all else fails, you can cement with scrap steel. Once cemented, all of the material can be well washed to eliminate soluble contaminants, then you can give the remains a wash in dilute nitric. I generally advise incineration before the nitric application, to insure that all chlorides are gone, and all of the carbonaceous materials that may be present have been eliminated.

Harold

 

[butcher]

dont think I would try to incenerate the evaporated solution of Aqua Regia, I believe alot of your precious metals would go up in smoke with acidic salts left, leaving only mixture of metal left. my guess nitrates (green color base metals)were possibly original problem, (I dont evaporate AR to crystal salt) (but after evaporating couple times adding HCl instead of urea)I would probably try Hcl and water to get metals and salts back into solution seeing what drops, Decanting, then cementing to a metal lower in series, sometimes I heat this with a copper chain (i use to collect gold) and to overburden a copper solution with copper, ,with this chain , then I let chain and solution sit cool in jar for week dropping metals lower in series than copper, decant brown powder, rinse my chain with a strong bleach HCl (save chain for next time it has gold plated and black gold spots which eventually all my chain copper will get disolved and gold collected)
this suggestion is just Ideas, to expand on. the good Advice Harold and Lasersteve have given

 

[Lino1406]

Shows "plenty of gold". explain