Black ap soultion

[Pteranadon]

Hello. I'm new here and to gold refining. I have put about 600grams of cut fingers into ap solution. The hcl 36% just covered the fingers in a 3L beaker and i then added about 200ml of 12% h2o2. It started bubbling went green and looked good. After a few hours it went black. Any ideas anyone? Any help would be greatly appreciated. Thanks.

 

[Shark]

Add an air source such as used in a fish tank or even a nebulizer, used by people with breathing problems, and let run until it turns green again. Loosely cover it so acid won't splatter all over the place as well. I would not add more H2O2 as I see it as a non renewable source of air and expenditure. You can just let it keep sitting until it turns green again, but it can take a fair bit longer.

 

[Pteranadon]

Thanks. I've set it up. Could you enlighten me as to why it turned black? I guess it is because the h2o2 was used up which is why you said to install an air pump.. i do however have loads of h2o2 and i don't mind adding more if it would do the same....

 

[Shark]

By adding to much H2O2 you risk dissolving some gold into solution. While this isn't a big deal, it can cause you to loose the visual sight of your gold. If you leave the H2O2/HCl solution until it turns green again, and all visible gold is gone from the boards, the gold that went into solution should drop back out. A stannous test would confirm whether the gold is in solution or not.

I would have used more AP in the beginning. I tend to prefer an excess of AP, (HCl and a very minimum of H2O2) When AP tends to go dark very quick it is a good sign of using to little to start with. It will still work most times, but it takes longer to finish up. When it turns black it used up the oxygen available to get the amount of work done. A quick test would be to take a plastic spoon full and add one or two drops of H2O2, if it turns green quickly, you know your oxygen content has been used up.

 

[Pteranadon]

Ahh, epic. I have done the spoon test and it did go green again instantly, thanks. I'll stick with the air bubbler. Also my stannous is a bit old but am i right in thinking that i can add some tin (sn) to hcl to make some more. I have that reacting now just in case it works. Thanks so much for the advice.

 

[anachronism]

Ahh, epic. I have done the spoon test and it did go green again instantly, thanks. I'll stick with the air bubbler. Also my stannous is a bit old but am i right in thinking that i can add some tin (sn) to h2so4 to make some more. I have that reacting now just in case it works. Thanks so much for the advice.

No. Stannous CHLORIDE is Tin with HCl. The clue is in the Chloride. 8)

Jon

 

[Pteranadon]

Hence the correction post post.

 

[nickton]

How can you tell you have a positive test when your solution is black to start with? Stannous will will turn black when positive. :mrgreen:

 

[Geo]

Dilute the dark solution with clean, fresh HCl until the solution clears enough to show a result. Stannous chloride is a definitive test and will detect minute traces of precious metal in solution.

 

[nickton]

thank you