Reupload: Preparation of Selenic Acid From Elemental Selenium

Please consider supporting this channel! Thank you! :-) In this video I carry out a superior prep of pure selenic acid from elemental selenium using a technique that I read about on atomistry's page about selenic acid (linked below). Crushed gray selenium is dissolved in HNO3 and the resulting mixture of HNO3 and H2SeO3 is oxidized using one of several reagents. I chose elemental bromine but chlorine can be used if steps are taken to prevent the HCl formed from reducing selenic acid back to selenous acid (HBr does not have this problem which is why I went with Br2 instead). Other choices are potassium bromate, potassium permanganate, or you could just dissolve selenium in chloric acid. Once oxidized the mixture is made slightly alkaline with ammonia water and then the selenate ion is precipitated out by addition of aqueous barium chloride. The barium selenate is filtered off (it filters very easily unlike barium sulfate), rinsed well, and then mixed with slightly less than the stoichiometric amount of 1.65M H2SO4 (any dilute strength is OK). The mix is heated, the barium sulfate filtered off (UGH!) and then the solution evaporated down at a temp of less than 120C to give pure aqueous selenic acid.

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