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4.1: Precipitation of group II cations
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After removal of group I cations, barium(III), cadmium(II), copper(II), and tin(IV) form highly insoluble sulfides that are separated by selectively precipitating them as sulfides in an acidic medium having pH range of 1 to 0.5. Calculations based on Ksp values are presented to prove that group III cations that form relatively soluble sulfides do not precipitate under these conditions.
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4.2: Separation and confirmation of individual ions in group II precipitates
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Tin(IV) sulfide is selectively dissolved in an alkaline medium and then re-precipitated as a yellow tin(IV) sulfide precipitate upon changing the solution to acidic. Then cadmium(II) sulfide is selectively dissolved in HCl and re-precipitated by neutralizing the acid with ammonia. finally, copper(II) sulfide and bismuth(III) sulfide are dissolved by heating with nitric acid, then the addition of ammonia turns the copper ion into a blue color solution, and the bismuth ion into a white precipitate
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4.3: Procedure, flowchart, and datasheets for separation and confirmation of group II cations
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The procedure, flow chart, datasheets, and filling instructions for the known sample that contains all of the group II cations and for the unknown sample that may contain some of the group II cations.