In this video we're going to make sulfuric acid by the oxalate precipitation method.

The idea is rather simple, oxalic acid produces insoluble metal oxalates with a lot of metal salts. But in doing so, the salt anions are left behind in solution and become their respective acids. So a metal sulfate can be converted into sulfuric acid by removing the metal ions with oxalic acid. The conversion isn't perfect, but it's good enough to give better than 50% yield under the right circumstances.

300g of Iron (II) sulfate heptahydrate was mixed with 1L of water and stirred until dissolved. Then 200g of oxalic acid with heated with 300mL of water until dissolved. The two liquids are mixed and iron oxalate precipitates out. This can be filtered but for improved yield, i found leaving it out in the sun to photolyze any dissolved Iron (III) oxalate for 8 hours increased yields by 10%. After filtration the filtrate is boiled down until it starts to crystalize and then cooled and filtered again before the filtrate is distilled at high temperature to get sulfuric acid. Effective yield was around 67%.

I wasn't able to get Magnesium sulfate or copper sulfate to work. I think magnesium sulfate just doesn't work, but copper sulfate produces ultrafine copper oxalate that can't be filtered.


Related videos:
Purification of Sulfuric Acid by Distillation:    • Purification of Sulfuric Acid by Dist...  



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