Determination of Trivalent and Tetravalent Manganese Oxide in Manganese and Reduced Manganese Ores

The methods for the determination of the trivalent and tetravalent manganese oxide in manganese and reduced manganese ores were examined. With acetylacetone the trivalent manganese ion forms a stable complex without any oxidizing action on acidified potassium iodide. In the presence of acetylacetone, manganese-tetrachloride, the resultant product of an ore sample dissolved in hydrochloric acid, loses chlorine and forms stable trichloride. The chlorine thus liberated chlorinates the acetylacetone, liberating iodine in an acid medium, if potassium iodide is present. Thus, by estimating the iodine liberated it is possible to determine the tetravalent manganese oxide in the presence of the trivalent manganese oxide. Although the method gives a positive error when the acetylacetone complex oxidizes potasium iodide if the acidity is high in a sample containing ferric iron, reasonable results can be gained if potassium iodide is added after the ferric iron has been reduced with stannous chloride. Hence the trivalent manganese oxide in an ore sample can be calculated by subtracting the value of tetravalent manganese, obtained as above, from the sum of trivalent and tetravalent manganese equivalent to the available oxygen obtained with ferrous sulfate method, as reported in Part 6.