What do you guys think about dropping with citric acid?

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dervishh said:
Yes, you're right!! It truly sucks at dropping!! So I just bought some of the good Ole trusty smb
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Refining mixed scrap is relatively complicated play in terms of chemistry "behind the scenes". Of course, all of it dissolves, it fizz some funky coloured gasses, in the end the powder is melted to yellow button, everything seems predictable, but there is plethora of situations when it simply isn´t :)

My point is - when something works very well (like SMB or any sulfite), stick to it. I don´t say that trying new alternatives isn´t good, but you need to bear in mind that it is best done with small samples which are expendable for you. So if anything fail beyond repair, you won´t lose significant ammounts of values.

Actually, I have tried, as professional chemist, thousands of reactions in fields of organic or inorganic chemistry, documented the stuff, learned, predicted, hypothesized and executed tweaked versions of the reactions to enhance their performance. It is tough game, and without good theoretical background, it will probably be unsuccessful - statistics are statistics. Educated guess is better than random guess and heavily theory based hypothesis is more likely to be verified and successfuly confirmed than random one.
 
Ascorbic acid does indeed work and really well on clean solutions but it can precipitate Pd if present if I remember correctly , I used it for years especially as a scavenger at the end of a drop and at that it’s excellent but the precipitate can be dirty so it needs refining again , I never used smb as I hated the fumes so I used ferrous sulphate as my main precipitator.
 
nickvc said:
Ascorbic acid does indeed work and really well on clean solutions but it can precipitate Pd if present if I remember correctly , I used it for years especially as a scavenger at the end of a drop and at that it’s excellent but the precipitate can be dirty so it needs refining again , I never used smb as I hated the fumes so I used ferrous sulphate as my main precipitator.
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Now my brain do not follow. Orvi writes that any suifide works and nickvc writes that he uses a ferrous sulphate. Could I then use pyrite to precipitate?
 
stella polaris said:
Now my brain do not follow. Orvi writes that any suifide works and nickvc writes that he uses a ferrous sulphate. Could I then use pyrite to precipitate?
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I think it has to do with Iron and its bonds within the Copperas.
It becomes “rusty” immediately after adding it.
 
stella polaris said:
Now my brain do not follow. Orvi writes that any suifide works and nickvc writes that he uses a ferrous sulphate. Could I then use pyrite to precipitate?
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All sulfites work. Sulfides are not a good choice.
Sulfite = SO3 2-
Sulfide = S 2-
I must confess that I hate english nomenclature of inorganic compounds :D It can be very confusing in certain situations, if you are not aware of all possibilities.
 
Yggdrasil said:
I think it has to do with Iron and its bonds within the Copperas.
It becomes “rusty” immediately after adding it.
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Yeah, iron (II) sulfate aka ferrous sulfate reduce the gold to metallic state by the action of Fe 2+ cations being oxidized to Fe 3+. Sulfate anion is just an anion, which isn´t touched in the actual reaction.

On the other hand, sulfites/metabisulfites like sodium sulfite (Na2SO3) or sodium metabisulfite (SMB = Na2S2O5) reduce gold to metallic state by the action of S(IV) in sulfite being oxidized to S(VI) = sulfate.
 
I love it when orvi gets to talking in technical terms. It then becomes a seriously real educational post. I know it takes time but some of us appreciate it very much.
👍
 
Shark said:
I love it when orvi gets to talking in technical terms. It then becomes a seriously real educational post. I know it takes time but some of us appreciate it very much.
👍
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Education takes time, that was the first thing I heared from my supervisor, who was supervising me during my study on college. Then I truly understood that when I was assigned the first bachelor student to co-supervise :) As master´s student, I did not get paid for that, of course, it was just my duty in the research group - and I know first hand as how much it can be exhausting, sometimes nearly frustrating. But I believe that if I can spread the knowledge, I should do that - because that is the whole point. If it does not feed me, and I am not reliant on secrecy in order to keep my business running and family fed and sheltered... I see no point why I cannot spend few minutes a day explaining something I know :)

Theory is essential thing in my opinion, if one want to understand and improve the process in targeted way. Doing it by chance can also work, but you need to accept the fact that it is (statistically speaking) a losing game :)
 
stella polaris said:
So can I use Pyrite (in theory) or do I have to oxide it first?
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Do not try a sulfide. A sulfide with an acid will give you hydrogen sulfide gas which is twice as toxic as HCN. In small quantities you will smell it like rotten eggs but in higher concentrations you will not smell it. It will paralyze your diaphragm muscles and make your last conscious three minutes a painful hell, it is not recoverable from h2s poisoning. You should see the precautions we take in organic synthesis any time hydrogen sulfide is used. Pyrite is why lots of prospectors books tell you that you never treat an unknown ore with acids.
 

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