aluminium heat sinks

[arthur kierski]

in cianide solutions(gold strippers) i used to add zinc powder to precipitate gold and some silver (sometimes present)----after filtrating out the gold -zinc powder i added nitric to eliminate the excess zinc and obtain the gold----i never knew when the process ended and because of that,i was many times unsure and repeated the process---sometimes the stripper solution had still gold in it--
Now, instead of zinc,i add to the solution aluminium heat sinks(5,5grams each) and make the solution more alkaline with naoh-----the aluminium starts to dissolve and precipitates brown gold powder, which one sees at the botton of the becker----- i found this alternative (for me) more secure and i am passing this experience to other members----
PS: i did also the experience with zinc metal and the dissolution(cementation) was not so efficient as it was with the aluminium----with the aluminium one can see the reaction going on and when bubble stops all the gold powder can be seen in the botton of the vessel---one filtrates the solution and withdraw the now thin al left over----
regards to all
Arthur

 

[goldsilverpro]

Thanks, Arthur,

Are you using a commercial stripper or, are you making up your own?

 

[samuel-a]

Yes Arthur

I'm using Al almost exclusively, both for acidic and basic medium.
Since too much Al might create pasty hydroxides, it is not so popular around here, therefore i do not advocate the use of it here.
I usually just eyeball it and stop the reaction once the solutions hold no more value, which is easy to know as you said, you can see whet there's no more cementation occurring.

Al (III) is also a good flocculant and help thing settle quite fast.

 

[arthur kierski]

Gsp,i am using comercial gold stripper---it stripps up to 8grams of gold per liter---i pay 100dollars for20liters of gold stripper----
regards and thanks for yours and Samuels remarks
Arthur