andyloris
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Separating Chromium(III) oxide from sulfides
Hi,
I'm new to the forum so sorry if I do any mistakes.
I recently bought some chromium(III) oxide from a pigment supplier, but when I tried disolving some in hydrochloric acid, A lot of gas with a rotten
egg smell was produced, probably because of sulfide impurities.
So how can i purify my chromium(III) oxide ?
Thanks in advance !
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woelen
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Probably you purify it quite well already by adding it to hydrochloric acid. Chromium(III) oxide is notoriously inert and will not dissolve in any
acid or base, not even when boiling. So, the sulfide impurity dissolves and the inert oxide remains behind. If you want to release the chromium(III)
from the oxide, then you need more extreme stuff. Molten NaHSO4 or molten NaOH will do the job. Both are extremely corrosive and cannot be handled in
glass. I personally think that chromium(III) oxide is quite useless for home chemistry experiments, because it is so hard to get it dissolved.
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andyloris
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Thanks, I saw on the wiki that Chromium(III) oxide disolves in acids, but didn't read after that | Quote: | | This material, however, is generally too unreactive to produce other chromium compounds. |
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clearly_not_atara
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Could try refluxing with KHC2O4 (potassium hydrogen oxalate)? This should give K3Cr(C2O4)3 which might be susceptible to reduction to a Cr(II)
compound or something. Sodium might also work, but be aware that sodium oxalate is poorly soluble.
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