Digesting with HCl Sodium chlorate

[4metals]

I have in the past digested finely divided karat gold scrap in Hydrochloric acid and sodium chlorate. Because of the small particle size of the atomized karat material the reaction is complete and very fast. Unfortunately atomizing metal is not en easy process nor is it cheap to buy the equipment.
I've been reading about the e-scrap guys generating foils by leaching away the underplating to loosen the gold plating but not to dissolve it. I have never personally done this and I was wondering if the high surface area of the foils would make it an easy digestion in HCl sodium chlorate.
Has anyone on the forum ever used sodium chlorate to digest gold?

 

[Harold_V]

If memory serves, Hoke suggested the addition of a few grains of sodium chlorate to evaporated gold when the process was carried to far and gold self precipitated.

I never tried it.

Harold

 

[4metals]

As usual Harold your memory serves you well, a few grains of sodium chlorate will re-dissolve any gold that drops during the 3x evaporation process to remove excess nitric. I think it would work on foils as well but I've never generated them to try it.

 

[Lou]

Sodium chlorate is an oxidizer, which happens to be clean (gives you the sodium salt of tetrachloroauric acid, which will reduce just fine). It can be used in lieu of hydrogen peroxide, air sparging from a bubbler, or sodium hypochlorite ("Chlorox")

It is easily made by electrolysis of brine solutions, and is quite cheap (perhaps more so than hydrogen peroxide).

 

[butcher]

would there be any chance that you would precipitate palladium from electronic scrap with the gold ?

 

[LittleJohnnyH2SO4]

Chlorate is just a means to generate chlorine gas in-situ. Think of it as water-free concentrated bleach for HCl-bleach processing.

6HCl + NaClO3 -> NaCl + 3Cl2 + 3H2O

In fact, you can make chlorate by boiling down bleach, but the process stinks, takes a long time, and tends to etch the glassware it's being done it. Lou has the right idea about building an electrolysis cell if you want to use lots of it.

Does anyone know if potassium chlorate is also "clean" or does it cause precipitation?
If it is "clean" and you only need very small amounts, a cell is a lot of work, so I recommend this procedure (which I wrote). The forum dictates that I put the mile and a half of warnings on it, so disregard them for the sake of sanity:

http://www.scienceforums.net/forum/showthread.php?t=37696