Bedlasky
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Zinc + acid = weird smell
Hi.
I did some reduction of molybdate in HCl using zinc. And I smelled something weird - similar to smell of H2S. Recently I smelled it when I reduced
chrome alum in HCl, but I thought that it was H2S because of sulfate reduction. But when I reduced molybdate, there wasn't any sulfate present. I use
the same zinc for reductions quite a long time and I never smell this "H2S" during reaction with HCl. It should be 99% zinc. Is there any common
impurity in zinc which cause this smell?
[Edited on 14-11-2020 by Bedlasky]
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ArbuzToWoda
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It's not sulfates that cause this, but sulfides. They're commonly present as iron sulfide and zinc sulfide in the zinc powder. Maybe your molybdenum
had such a contamination too, you don't need more than a couple hundred micrograms of it to cause such a smell, as our receptors are very sensible to
hydrogen sulfide.
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MidLifeChemist
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Interestingly, this subject is discussed in this paper from 1861
https://sci-hub.do/10.2307/25057965
Some interesting observations (not all related to that paper) - it appears that the main impurity in Zinc is Lead. Also, most Zinc is smelted from
Zinc Sulfide. Last, but not least - the odor of H2S can be detected at 130 parts per billion.
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