Has anyone actually measured the purity?

[GregerG]

What kind of purity can one expect from using the SMB in auric acid method?
and compared to using oxalic acid?

(I've read 995 for SMB and 999.5 for oxalic methods - is there any truth to that?)

Has anyone _actually measured_ the real purity with _professional_ equipment?
Or is it only guess-work...

It would be really interesting to actually _know_ the purity, for instance if you refine it once or twice, if you use tap water or destilled water, using urea or not, etc...

 

[4metals]

Purity depends on technique as much as chemistry. Oxalic drops are more difficult because the solutions have to be hot. SMB drops gold close to .999 on a single drop which have been verified by ICP. Sulfur dioxide drops the gold closer to .9995.

Rinsing is important for purity as is not adding excesses of precipitant. Keeping the solution cold before filtering also helps eliminate silver from the fine gold.

 

[Lino1406]

The difference between "oxalic" and "SMB"
is only the color - gold for the 1st, red chockolate
for the 2nd.

 

[goldsilverpro]

IF! you use proper procedure and do what you should to get the silver chloride and lead out before dropping the gold, plus good leaching and rinsing of the gold powder, you should get at least 99.95% purity gold with SMB or other sulfite. At least, I always did. In those rare cases when you melt it and you can visually see it is slightly off purity, a small pinch or 2 of borax and maybe a prill or 2 of niter will usually bring it up to snuff.