Cleaning precipitated gold powder

I read advices to boil precipitated gold powder in hydrochloric, nitric, sulfuric acid, wash with ammonia and use more substances. What do you think about boiling precipitated gold powder boiling in HCl, where several drops of nitric are added (such a very weak AR)?
Till this moment I boiled the powder in HCl, but after some thinking decided, that very weak AR is better to use, as HCl, because HCl have no deal with copper, palladium, platinum and much more materials, which could be captured precipitating gold from not very clean solutions.
What do you think about this?

Not a very good idea. Follow the washing procedures laid out in the forum.

3 Boils in water
3 boils in HCL
3 boils in water
3 boils in ammonia
3 boils in water
3 boils in nitric
3 boils in water

And don't forget about your incineration during the process.

then refine your 2nd time= pure, pure gold

My personal opinion, after practicing what I've learned here, is never to add nitric after going to the "trouble" of getting rid of it. You would be dissolving some of the gold again, & now you'll have to drop again; to add more nitric on & on & on.

After AR reaction is over, most of the silver would be on the bottom; now I add some sulphuric to the solution so any lead in the solution drops. Filter the solution & drop with SBM. Wash as recommended, 3 boils in water; 3 boils in HCL; finally 3 0r 4 boils in water & dry. I see the difference in how much lighter the color of my gold got. (A wash in ammonia, added to this, if you suspect ag still in the gold powder.)
I learned here that HCL DOES deal with copper, that's why its use for the wash; & most of your PGM's should still be in solution to be dropped...

pHIL

I agree with Phil, no nitric.

I use three hot water rinses-settle-siphon, then 1 boil in HCl-settle-siphon-test liquid with stannous, then three more hot water rinses-settle-siphon-dry. Refine a second time in AR-cool with ice-filter clear and repeat wash cycles.

Steve

precipitated gold have some impurities that mechanically dragged down with it, and they will be gone after HCL boil.

gold powder do not act as melted piece, and even might dissolved in HCL boil, test it next time you wash gold with HCL.

always test acid washes

samuel-a said:

gold powder do not act as melted piece, and even might dissolved in HCL boil, test it next time you wash gold with HCL.

always test acid washes

Click to expand...

If you have completely neutralized,expelled,or used up,all of the nitrates in the AR then there should be no problems with gold being digested with a clean Hcl boil.
I have never had a wash come back positive,unless there was a mistake on my part before I started washing.

mic

I'm referring to only minute traces of gold, probably nano-scale particles.

i do wash properly with water before HCL boil, and still it is faint positive color.
To proof that, I've tested different levels of contaminated dropped gold that have been washed well with water, and it seems, that the dirty the drop is, the more tendency of the gold show up as well in the test...
can't explain it though....

I have said this before, always test your washes and rinses, plain HCl can digest gold. As part of my gold refining routine I take my once refined gold powder (after washing) and place it on a hot stir plate in HCl to re-digest it for precipitating a second time.

Oz said:

plain HCl can digest gold. As part of my gold refining routine I take my once refined gold powder (after washing) and place it on a hot stir plate in HCl to re-digest it for precipitating a second time.

Click to expand...

In 6 years I have never once seen common muriatic acid digest refined gold,whether its boiling or not.
Do we need to rewrite Hoke and the forum handbook?

mic said:

Do we need to rewrite Hoke and the forum handbook?

Click to expand...

maybe... 8)

Edit:

here is the stannous test of the HCL washes from my last inquaration :


it's hard to tell by the picture, but trust me, this is purple, and the powder washed well with platy of water.

Considering my personal experience and the experience of others I know,and the forum handbook,and Hokes,which all contributing members swear by,I think I stick with what I know.No offense.

samuel-a said:

it's hard to tell by the picture, but trust me, this is purple, and the powder washed well with platy of water.

Click to expand...

Then you still had residual nitrates on your powder.This is why harold preaches to incinerate.You can wash it with boiling water a thousand times and still have residual nitrates.

Certainly worth a stannous test.

I have experienced positive tests in the HCL rinse. Powders from dirty solutions being the worst offenders. I wouldn't recommend skipping the rinse by any means, just know it needs to be saved, perhaps used in the next AR batch.

qst42know said:

Certainly worth a stannous test.

Click to expand...

I agree whole heartedly.
but as I stated before I have never experienced a positive result unless it was my fault.

Even still, can't you see how that using the method Oz does would save a few steps, time, and chemicals?
Notice he said with a stir plate. That means he probably has a stir bar.
Well, actually I know he does. The rapid stirring must introduce enough oxygen from the air to oxidize the gold.

Whip in some air to make oxygenated HCL?

looks like

Actually we have had this exact conversation before,and you may be correct about the stir bar,though I highly doubt it introduces that much oxygen,however it does not have any bearing on the former conversation.

Could be using tap water with chlorine in it.. :!: :?: :arrow:

Mic, why do you doubt him (Oz)?
The guy does more refining than you may realize.
You should try it. I don't have a sutible stir bar at the moment.

If you are worried about straying from the original posters question we could delete all the posts after Steves.
He gives his method and He mentions testing the washes.