thio leaching question

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Wyndham

Well-known member
Joined
Nov 29, 2007
Messages
111
Location
Seagrove NC
From the little I've found so far on Thio leach agitation seems to be needed. How about a rubber or ceramic rock tumbler? and since it also seems that air is needed, would peroxide added to the thio work or hinder.
If anyone has a recipe for the thio method please let me know, Wyndham
 
The sponge gold (99.92 % pure) has been leached with ammonium thiosulfate solution. In this investigation, the gold leaching rate (extraction rate) and the thiosulfate oxidation rate (consumption rate) have been studied on the effects of CuSO4, (NH4)2S2O3, (NH4)2SO4, NH4OH, stirring speed and retention time. The copper ion acts as a catalyst in gold dissolution, on the other hand, it also accelerates oxidation of thiosulfate (consumption). It was found that the best gold extraction was obtained at 12 hours under following optimum conditions:0.8 ∼ 1.0 mol / l (NH4)2S2O3, 0.03 mol / l CuSO4, 2.0 ∼ 3.0 mol / l NH4OH, 0.4 ∼ 0.5 mol / l (NH4)2SO4, pH 10 ± 0.2 and 150 rpm. The thiosulfate oxidation is about 15 % of the initial concentration.
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Can anyone comment on this. I don't know chemistry but this seems to tell what needs to be used.
The chem ref seem to be ammonium sulfate, copper sulfate, sulfuric acid??? and ammonium hydroxide. This is from the WIKI ref for the formulas. Could someone break this down to a more understandable method.seeing this method.
hope to hear from someone, Thanks Wyndham
 
Brandt has posted that he uses ammonium thiosulfate or "fixer".
You could start with sodium thiosulfate and add household ammonia with a little copper sulfate as a catalyst. I have read that iron also acts as a catalyst, therefore with some ores the copper may not need to be added.
 
Thanks, I'll have to find a photo supply in a bigger town than what's near me about 50 miles away. Good project for next week. Thanks Wyndham
 
Randy: You didn't tell me you read about the combo of thio/cu sulfate/ammonia. Could I relieve you of your source ? Apreciate. Phill
 

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