![]() ![]() People who don't know what they are doing and only mimic something they have read or watched on youtube often talks about neutralize nitric acid and so the misconception is perpetuated.īoth SMB and iron sulfate is quite selective for gold, although there are some quirks with both chemicals. We don't call it neutralize to remove nitrates from a solution, we call it denoxing a solution. To truly neutralize acid you need a base. You never neutralize by dilution, you only dilute your acid. Sorry if I've been a bit long but it's exciting actually and I have a lot of questions in waiting -) Should it not just be more easy to only use Iron Sulphate II ? Now one more question I also once used Iron sulphate mixed with water +- 2x the AR volume and I added it to the AR then I added 2x the initial AR volume again water and I got very faster precipitation from the gold.įollowing what I understand with the Iron Sulphate it will precipitate any metals and with SMB only the gold.īut in my case I remove all metals already with the Nitric and water bad I make to get the gold off the PCB so is it really needed to use Urea and SMB to make this job ? ![]() I completely agree this is also what I was thinking and when I did add the SMB there was a bad smell of sulphur not sure it was normal.But I dont know the PH I need to have before adding the SMB.Īnd following my idea add more regular city water with high PH should neutralize more the acid reason why I added finally so much water and 24h later when I added again SMB I got the precipitation. I rarely have a problem with gold precipitating nowadays and I rarely wait more than 5 minutes until I pour off the clear liquid in my stock pot. Personally I think about 5-10% HCl (only guessing, never measured though) is a good concentration to drop gold with SMB. The gold particles have to aggregate into heavier particles until they are large enough to sink and in a dilute solution it's fewer gold particles in same volume so it just takes longer time. To precipitate gold from a diluted solution takes a longer time than from a more concentrated one. Your problem was probably too high pH and a too diluted solution. But too weak and the SMB only dissolves and doesn't release any SO 2 that actually precipitates the gold. With too acidic solution the SMB turns into SO 2 gas immediately and never dissolves into the liquid so it is mostly wasted. On the other hand I've had real problem to precipitate gold from almost neutral gold solutions and I had to add more HCl to get it to drop. I've precipitated gold with SMB from really acidic solutions like pure HCl and it works. I'm not PoA but I'll give you an answer anyhow. I added a picture to show how it look the black marks were there before, it's not the new gold. Thank you for reading, any help is welcome -). Since I'm a beginner, I do several tests and when I don't use urea and no SMB and I just add a mixture of water and iron sulphate II to the aqua regia the precipitation works.īut really wanting to understand why with urea and SMB it doesn't work I tried again but nothing to do no gold precipitate.įinally I tried as a last resort to add iron sulfate II but this time the liquid did not turn black but orange with a sulfur smell and after 2 hours it became very clear againĬould someone tell me where I made the mistake and if it is still possible to recover the gold in the solution I have? Then I said to myself that maybe the neutralization was not done, so I added water and SMB again without success. Then I started to add the sodium matabisulfite SMB, after the first spoon the liquid became transparent I kept on adding SMB 3 spoonfuls even 4 without success impossible to make the precipitation of gold. I added +- 4 or 5x the volume of distilled water and 3 spoons of urea which I dissolved well to neutralize the solution. I dissolved my gold in it then filtered the solution which was quite yellow. I made a mixture for the aqua regia of 25Ml nitric acid at 60% + 75Ml hydrochloric acid at 30%. I started by removing the gold from the components in a mixture of 50% nitric acid at 60%+ 50% distilled water. I have a concern about the precipitation of gold with aqua regia and no way to understand what I am doing wrong. I am new on the forum but I already spent many hours reading a lot of posts -) ![]()
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