Gold with Tin

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hrushi

Well-known member
Supporting Member
Joined
Dec 15, 2008
Messages
89
Location
india
Hi Guys

I have got gold dust mixed with Tin(10%++ wt.) copper silver, etc..
Dissolved in AR then precipitated with HH, violet clouds formed those cannot be filtered so had to do gravity filtration on cloth, much of it has gone down.
How to recover gold from this. Tin is creating problem here, gold is converted to colloidal


Regards
Hrushi





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That tin really seems to be quite a bugger for gold refiners.
Hello hrushi. I am new to recovery & refining, but I have read about, and seen pictures of similar situations. I think you have created the dreaded meta stannic acid! Most refiners will rid their material of all base metals before refining, if possible. They seem especially leery about tin. Tin makes the blue-grey mud that is an unwelcome sight in anyone's filter paper. Use the search option to research metastannic acid or meta stannic acid. I have read that some people roast the mud in an oven first, then they are able to dissolve the tin away later. That process may only help with liberating foils, I don't know, but the search option should help while you wait to hear from a real refiner.

Good Luck!
mike
 
hrushi said:
Hi Guys

I have got gold dust mixed with Tin(10%++ wt.) copper silver, etc..
Dissolved in AR then precipitated with HH, violet clouds formed those cannot be filtered so had to do gravity filtration on cloth, much of it has gone down.
How to recover gold from this. Tin is creating problem here, gold is converted to colloidal


Regards
Hrushi





View attachment 51202
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Your major mistake was the AR, as war child says.

Tin and Nitric are not very compatible in our line of work.

If I’m not mistaken the roasting transforms the Tin so you can dissolve it in HCl.
LYour problem is the colloids, but that should not be more than a milligram or less.

If you still want to chase the colloids try adding ordinary salt and heat it, and stirr vigorously, maybe you can form larger colloids that may be filterable or can sink.
I don’t know for sure that it will work though.
 
I would evaporate the whole lot to dryness without filtering as collides will go thru most filters so you will have some trapped in the tin and some that will go with the liquid.
Evaporate till dry then roast the solids 30-60 minutes at dull red should convert all tin paste back to metallic tin. Then dissolve all tin with HCL heating will speed up this step. Once everything HCL will dissolve is gone wash then roast remaining solids. Then go to nitric to remove any silver. Then AR for gold.
 
This is the kind of precipitate I get when I was diluting my gold chloride solution with too much water before precipitation with ferrous sulphate
I'm not sure about this but can't he boil the precipitate in dilute sulfuric acid to convert the tin to water soluble tin sulphate that can be removed by rinsing with hot water (CM Hooke).
 
Saddiq NG said:
This is the kind of precipitate I get when I was diluting my gold chloride solution with too much water before precipitation with ferrous sulphate
I'm not sure about this but can't he boil the precipitate in dilute sulfuric acid to convert the tin to water soluble tin sulphate that can be removed by rinsing with hot water (CM Hooke).
Click to expand...
Can dry roast, crush, and cupel with a basic flux. Clean the gold button and hold for future PGM processing, if necessary. Also, hold the cupel itself for parting the values in it
 
Yggdrasil said:
If you dissolve the Tin in HCl first there will be no need for dealing with metastannic acid.
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Based on my experience it's not always possible: when I work with bronze material (e.g. spring contacts from connectors) there's always a bit of metastannic acid produced. Amount of tin is based on type of bronze. After HNO3 I got used to dilute with warm distilled water, then filter through series of mesh nylon filters with different finesses (between 300 and 60 µm). Finally I filter the filtrate through ordinary paper filter where remaining Au + metastannic acid is captured. I let the filter dry and save for later processing.
 
Hombressino said:
Based on my experience it's not always possible: when I work with bronze material (e.g. spring contacts from connectors) there's always a bit of metastannic acid produced. Amount of tin is based on type of bronze. After HNO3 I got used to dilute with warm distilled water, then filter through series of mesh nylon filters with different finesses (between 300 and 60 µm). Finally I filter the filtrate through ordinary paper filter where remaining Au + metastannic acid is captured. I let the filter dry and save for later processing.
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OP mentioned Gold dust with 10% Tin.
So I envisioned a mix not an alloy.
On the other hand it may be preferential to use HCl/Peroxide to dissolve the Gold since it is dust.
Thus circumventing the whole issue😏
 
Yggdrasil said:
On the other hand it may be preferential to use HCl/Peroxide to dissolve the Gold since it is dust.
Click to expand...
The size of the dust particles determines how effective alternative digestion methods are, one man's dust is another man's chunks. Very fine dust, under 60 mesh, can dissolve by alternate means but larger particles become less effective.
 

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