Gold refining?

[El_Zorro]

Does anyone have any info, links to information on refining gold ad platinum with aqua regia?  I have a pretty good idea of the overall process, but I don't have the fine details down.  I know that the gold, platinum, etc. is dissolved in the aqua regia, then all junk pieces are removed.  Then various chems are added to precipitate the various metals.  I know that ammonium chloride is added to precipitate the platinum as ammonium chloroplatinate, and apparently sodium/potassium metabisulfite is added to precipitate the gold.  But I also saw somewhere the urea is added before the metabisulfite in the gold extraction process, does anyone have any more details than that?  And what is used to precipitate palladium?

[abolt]

Doesn't Palladium and Aqua Regia make Palladium Chloride?
I hope it does as swim followed this and ended up with something very similar in looks and texture but has not "wacked" it yet.

Post 376915 (missing)

(Hammer: "Here is the text of an old write up, this might ...", Chemicals & Equipment)
Please take into account

Post 398891

(abolt: "Using a cheap Hydroponics inline fan as a fume", Methods Discourse)

[abolt]

Also, I once heard that reacting Platinum and Aqua Regia in a similar fashion as the PDCL2 synth. would get you Chloroplatinic Acid.

[calcium]

I hope this helps, there seems to be a bunch of proprietary supplies involved, but it'll work.

http://ishor.com/refining.htm

[PolytheneSam]

Palladium will dissolve in nitric acid.

[El_Zorro]

Yeah, if you chunk a bunch of old computer contacts and parts in aqua regia, then all of the gold, platinum, and palladium will go into solution.  If you add a conc. solution of ammonium chloride, then it will react with the formed chloroplatinic acid to precipitate as ammonium chloroplatinate, which can be used to make platinum dioxide, which is an extremely efficient hydrogenation catalyst.  If you add some other chems, the gold precipitates as a nice little legal profit for you.  The palladium will form palladium chloride, which we all know what that can do.  I'm not sure how to precipitate it from the solution to get a reasonably pure product, but I'm sure it can be done.

I'll check out that link, though, thanks.

[El_Zorro]

Well, I did find out some shit about it.

So you dissolve everything in your aqua regia.  Then you add urea, which neutralizes the nitric acid without neutralizing the HCl, which keeps everything in solution.  Then you add your ammonium chloride, and see if you have any platinum.  Then you add some sodium metabisulfite, and your gold precipitates.  Then you add some sodium chlorate, slowly!  And your palladium precipitates out.  I'm not sure what form the palladium is in, maybe PdO??

I don't know just how safe the chlorate part of the procedure is, because any contact a chlorate has wit an acid forms chloric acid, which explodes on formation.  So I guess there might be enough water in the solution to keep it stable long enough to react with the PdCl₂, who knows?  So I guess just add it very slowly, a little at a time.