Oxalic acid

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Oxalic acid, (C2H2O4), is an organic acid found in some plants, for example rhubarb. In refining it is used for precipitate gold from solution. It demands a bit more work to use compared to SMB or copperas but has a reputation to produce very clean gold.

Oxalic acid is also used in lanthanide refining.

Contents

Precipitating gold

( Main article : Precipitating gold with oxalic acid)

Oxalic acid can be used to precipitate gold from solutions. It is a good precipitant to separate gold from PGM:s in solution. It has a slight drawback of also precipitate tin and copper, but if SMB or sulfur dioxide is used in a second refining a lot of the contaminants can be removed. Instead of a second refining, good washing can be used to remove any contaminants.

It is also used in bromate hydrolysis to remove gold from platinum solutions.

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Safety

Oxalic acid has a LD50 of 0.6g/kg, a lethal oral dose is about 15-20 grams. The toxicity comes from precipitated calcium oxalate in the kidneys, leading to kidney failure.

References

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