# materials with precious metals



## Jim H (Dec 12, 2012)

I do materials using the more or less Igoli system. I try to pull out the gold by using a HCI and Chlorine leech, recovery with metabisulphate. It seems to work okay as I crushed lots of material very fine,let the HCI and Chlorine do its job over 3 or 4 days, then extract the fluid, filter, and the metabisulphate. My question is this: I am getting a little gold in the leech, but am also getting lots of silver. Once I have filtered the product and washed it 3 or 4 times to neatralize the acid, I try and get the silver out of the material. I then put the material in Nitric Acid at which time about 3/4 of the material dissolves. The material is then filtered. The liquid coming off of the Nitric is a very bright yellow. What is this material that is yellow. Is it silver, copper, zinc etc. I put a piece of copper in it and its changed to a dark blue. Is this cementing the silver out of the solution.? Like to hear from a person who knows what I'm talking about. The solid material seems far more like gold now so, I feel it may be working. Like to recapture the gold and the silver would be nice to. Thanks


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## gold4mike (Dec 12, 2012)

Questions:

What is your starting material?

How are you dealing with base metals?

Are really using Metabisulphate rather than Metabisulfite for a precipitant?

Have you discarded any left over material?

Most of your PM's have probably cemented out of solution onto any remaining undissolved metal in the reaction vessel.


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## Jim H (Dec 12, 2012)

Its actually metabisulphite(spelling error). The material is crushed gravels containing gold , silver, copper, zinc, etc. Many metals. According to the Igoli leeching method the majority of small metals should be dissolved and in the leach. Do you think that I am cementing a lot of materials from the leech to the materials, before extracting it out? Maybe this is a bad method as chloine leeching isn't used much any more. Also gravity seperation isn't much use, because a lot of the rocks going out the table, into the tailings, have very fine metals attached to them. I thought leeching the whole thing twice would increase my results,and it has. Like I said though I recover lots of metals with the greatest being silver. I can eliminate this and the majority of the other metals with nitric acid. The nitric acid turns a bright yellow when filtered, and the material I'm left with is a more purer gold. Just wondering why the liquid is so yellow and thoughts on what metals it would contain to make it this colour?


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## gold4mike (Dec 12, 2012)

I apologize - I was unaware of the Igoli leaching method for ore and I process only escrap.

My statement concerning cementation of values onto base metals is most likely way off base for what you are doing.

I'll defer to the experts for your answers.


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## Jim H (Dec 12, 2012)

Thanks gold4mike.


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## Geo (Dec 12, 2012)

actually Mike, its not that far off track. most ores contain iron in some form. as we all know,iron will precipitate all metal that is higher in reactivity.iron in almost all forms will react this way (oxides,chlorides,sulfates).


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## Jim H (Dec 12, 2012)

Geo, I know you wrote this comment in 2011. I forgot to add that prior to the leach, I soak the materials in a 50/50 HCI and H2O solution. According to the Igoli method this is suppose to rid the leach of a lot of the iron and sulfur content. I pour this off prior to the actual chlorine and hydrochloric being added. Also the longer it sits with the odd bit of stirring now and then and a little chlorine maybe being added for oxidation, it seems to have much better results. Do you think why the nitric acid which I used to dissolve the silver etc. maybe is so yellow because of such a large amount of iron in the material. This definetly would explain the nitric being so yellow. Thanks


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## Geo (Dec 12, 2012)

most acids will discolor when add an oxidizer. hcl will yellow when you add Cl with nothing else in the mix. color is not a very good indication of material content. stannous chloride is a very good indicator. 

did you roast the ore before treating with chemicals. did you mill the ore before you treated with chemicals


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## Jim H (Dec 13, 2012)

Geo, I cruedly had a 24 hour bonfire going on top ot the material, not only to dry it out ,but like you said to maybe help burn off some of the sulfur etc. I then crushed the material to about a 40 mesh. I'm sure some of the material being closer to a 300 to 400 mesh. I have a crusher roller machine so it really gets it fine. Like you said the chlorine and HCI turns a yellow colour when mixed. Then I metabisulphite the filtered product from concentrates. I then distill wash it 3 to 4 times. Then I nitric acid the powder on a low heat for about 2 hours. A lot of the other metals especially the silver dissolve into chloride and I filter this of. The product left behind is not a 99% gold but it is getting close,and looks much better than prior to using the nitric acid to remove the many contaminates. Do you figure why the liquid coming out of the nitric wash is so yellow because the metabisulphite is dragging a lot of iron with it. Its definetly not gold as the stannous test proves negative for gold. Does metabisulphite in reaction with the concentrates, usually solidify such a big amount of iron. If it is iron though this would I'm sure explain why my liquid nitric acid is so yellow. Would you agree?


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## Jim H (Dec 13, 2012)

Geo, I think I found my answer. The nitric acid upon reaction with the contaminated metals in the powder is absorbing nitrogen dioxide. This would explain the yellow discolouration. Thanks for all your help in this matter.


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## Geo (Dec 13, 2012)

to help stop chlorides from forming when your moving from one acid to the other, try incinerating between processes.its the only way to remove either acid completely.


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## Jim H (Dec 13, 2012)

okay thanks Geo, I will give it a try.


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