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5.1: Separation of group III cations
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After insoluble chlorides and acid-insoluble sulfides of group I and group II has been removed, the medium is made alkaline at pH ~9 where group III cations precipitate out as hydroxides, i.e., iron(II) hydroxide, iron (III) hydroxide, chromium(III) hydroxide, and nickel(II) hydroxides. These ions also precipitate out as insoluble sulfides in the alkaline medium.
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5.2: Separation and confirmation if individual ions in group III precipitates
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Nickel sulfide is separated based on its insolubility in HCl, then dissolved in aqua regia and confirmed by making a red precipitate of its complex. Iron(II) ions are oxidized to iron(III), dissolved in HCl, and confirmed by making a red color complex. Chromate ion is reduced to chromium(III) ion by acidic hydrogen peroxide, then confirmed by precipitating it upon making the medium alkaline.
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5.3: Procedure, flowchart, and datasheets for separation and confirmation of group III cations
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The procedure, flowchart, datasheets and filling instructions for the known sample that contains all of the group III cations and for the unknown sample that may contain some of the group III cations.