When calibrating the potassium ferrocyanide standard solution, what is the role of adding ammonia to the zinc oxide solution and then dropping in sulfuric acid?
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When calibrating the potassium ferrocyanide standard solution, zinc oxide is dissolved using hydrochloric acid and then the volume is adjusted. A portion of this solution is taken, water is added to it along with ammonia to produce a white gelatinous precipitate. Then sulfuric acid is added drop by drop, and the mixture is heated to 70–80°C; subsequently, it is titrated using potassium ferrocyanide. In this process, what are the respective roles of adding ammonia water, sulfuric acid An, and sulfuric acid?
What is the purpose of heating to 70-80°C as well?