tin +lead +au powder

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arthur kierski

Well-known member
Joined
Feb 10, 2008
Messages
1,119
Location
são paulo---brazil
from my work i make a type of stock pot with the liquids from which gold ,silver ,pd rh was extracted-------after some time ( 3 to 4 weeks) i add to this solution iron powder which precipitates many base metals with some precious metals -----this stock pot solution have almost no copper which wsa extracted before with nitric----my last liquid have much tin and pb which was precipitated with iron and the powder is not magnetic----to this powder i took a sample and tried to dissolve in ar------the ar liquid showed gold with stanous chloride --but it did not dissolve most of the powder-----
question:i have 250grams of a powder containing gold,sn ,pb---how should i extract the gold from these miscelanous?
thanks for any advice----
note :this tin was dissolved first in hcl as a pre process and the liquid became purple like colloidal gold----
 
Why do you precipitate with Iron? I would roast the sludge first to drive off any oxides and help it dissolve better. Crush it up so it has more surface area to help the dissolve. Try and get a complete dissolve in Aqua Regia, add as little nitric as possible to get the job done and filter it, then add copper to kill off the nitric and saturate the liquid with copper. The copper will drop out the gold and leave behind the tin and lead. You kind of do a reverse stannous chloride test. When it all dissolves it should test positive with stannous, then you add the copper and test it as the copper dissolves until all of the gold is dropped and it won't test positive for gold. The lead and tin will still be in solution and your gold and any other PGM's are on the bottom, filter it and refine it as usual to clean it up.

This works because of the position different metals have on the electromotive series chart. You seem to do a lot of different types of material, you should have a chart of the electromotive series of metals hanging on your wall. simply stated, if you have a mixture of different metals dissolved in solution, look at the chart and know that any metals above the metal you choose to precipitate with will stay in solution and those below will drop out.

If you have an assay furnace another option would be use a giant cupel, often sold as commercial cupels, they hold up to 30 pounds of lead. Just mix your dried mixed metal powder with granulated lead and put it on a preheated giant cupel and keep it at 1000 C until all of the lead i adsorbed aong with any base metals leaving you a bead (hopefully golf ball sized) of gold and any other PGM's in the mix.
 
4metals, i do not have sludge to roast----as i said i have a solution which after using iron powder precipitates the sludge-----this precipitated sludge +ar dissolves very little but the ar solution indicates gold with stanous chloride---i deduce that i have more gold in the powder(sludge) and the help that i asked is how to separate the gold from tin and lead----by the way,i did roast the sludge (powder) obtained and then i used ar which did not dissolve the sludge----mark, i will look for comercial cupels(although i am looking for a chemical solution)----i already (before going home) left the sludge in full strenght hcl(trying to dissolve the lead) and then dissolve the tin
 
Try cementing the gold out with copper. I do not know if the copper will cement out the gold which is bonded to the tin. The next time you have this stuff dried you can leach the lead with nitric or sulfuric. Tin will dissolve in sulfuric as well so I'd use all sulfuric to leach both at once.

Theres a good chance you have gold stannate in solution now, it is made from tin, gold and oxygen. (or from gold and stannic acid) Its a nasty hard to filter snotty mess. Roasting will drive off the oxides and give you a leach-able product again.
 

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