Talk:Marsh test
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False positives due to other main group elements edit
As far as I know, several other main group metalloids can give positive test results as well, like Sb, Bi, Se, Te, Ge... Especially so if magnesium is used as the reducer instead of zinc. On the other hand, these can readily be distinguished from As by subjecting the precipitate to further testing. Arsenic dissolves in an aqueous solution of hydrogen peroxide and ammonia. Also, more metallic elements like Bi or Sn should produce a silvery precipitate, not a black one. I would expect selenium to produce a red precipitate, but I'm not an expert.
I wondered why there is no mention of possible misidentification in the article, although I've heard about that in TV documentaries. 2003:E7:7706:7A06:4B1:8B7B:7E86:EF8E (talk) 22:38, 11 July 2022 (UTC)
- Read again. Sb and Bi are mentioned, as well as methods how to distinguish them from As. --2003:E7:7706:7A06:4B1:8B7B:7E86:EF8E (talk) 22:49, 11 July 2022 (UTC)