Abstract
In this experiment the following results were obtained. 1. NH_4-salt is usually contaminated in cobaltnitrate reagent, and it makes the experimental results irregular. 2. The cobaltnitrite precipitate warmed at 60℃ for one hour gives the same result without reference to the period to settle the precipitate at room temperature. 3. A little asbestos does not decompose KMnO_4 solution appreciably. Therefore it is better to treat the cobaltnitrite precipitate as follows. The p p t. is filtered by means of filter-stick with asbestos filter mass, followed by dissolution with conc. H_2SO_4. The H_2SO_4 solution containing asbestos is poured into excess KMnO_4 solution, the excess KMnO_4 is determined as usually.
