Group 3 Base-Insoluble Sulfides and Hydroxides

and Ni. In addition, the additional base causes Cr , Fe +, and Al to precipitate as hydroxides. After the solid is separated from the liquid, the solution is ready for the next step. 

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Group 3. Base-insoluble sulfides and hydroxides After the solution is filtered to remove any acid-insoluble sulfides, it is made slightly basic, and (NH4)2S is added. In basic solutions the concentration of is higher than in acidic solutions. Thus, the ion products for many of the more soluble sulfides are made to exceed their K p values and precipitation occurs. The metal ions precipitated at this stage are Al +, Cr Fe +, Zn +, Ni +, Co +, and Mn + (The Al +, and Cr ions do not form insoluble sulfides instead they precipitate as insoluble hydroxides, as Figure 17.23 shows.)... 

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