Messages Archive

rest of the chemistry story
Response To:
the source of Cr(VI) ()

Bill Tindall, E.Tn.
Iron ore that contains chromium oxide (CrIII) is smelted with a mix of carbon and limestone at very high temperature. Calcium silicate and calcium oxide are formed and float to the top of the iron melt.

Chromium prefers to be extracted into the slag. Under these basic conditions (both calcium salts are highly basic), and exposure to oxygen (the top of the melt will be exposed to air) the chromium will oxidize to Cr(VI) to form calcium chromate. (dichromate is formed by acidifying any chromate solution, but both are Cr(VI) )

I can't imagine any slag contains much chromate or it would be recovered from the slag to produce chromium metal.

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