Study on the sample dissolution method for determination of ferrous oxide in chromite

This paper proved that after pretreatment by boiled sulfuric acid wetting combustion(about 330℃),chromite went through a series of changes,including phase change,formation of chromium sulfate,enhancement of chemical activity and inclination to dissolution reaction with phosphoric acid,all of which improved sample dissolution in the determination of ferrous oxide in chromite.The sample was firstly mixed with vanadium(Ⅴ)-vanadium(Ⅳ) solution and sulfuric acid,heated on electric furnace(2 000 W) until thick sulfur trioxide smoke appeared and soared for 1-3 min.Then,the condensed phosphoric acid was added.The solution was heated until thick smoke appeared and soared for 3-5 min.The obtained solution was properly cooled and diluted.The residual vanadium(Ⅴ) was titrated using ammonium ferrous sulfate standard solution.The content of ferrous oxide was calculated by blank experiment.Meanwhile,the function of wetting combustion method with sulfuric acid and the reaction mechanism were discussed.The proposed method has been applied to the determination of ferrous oxide in chromite.The comparision of the analytical results of certified reference material and production sample indicated the results were satisfactory.