Method improvement on Determination Mass Fraction of Fe in Cryolite

In a beader,the cryolite sample is heated to smoke with concentrated sulfuric acid,then dissolved to clear solution with chlorhydric acid.Fe 3+ in the solution is reducted to Fe 2+ using hydroxylamine chloride.In acetate buffer solution,Fe 2+ combines with o naphthisodiazine to form red complex.Mass fraction of Fe in the cryolite can be determined by determining mass fraction of Fe 2+ in the complex.The method is simple and quick,and can be used to determine mass fraction of Fe in cryolite.