Determination of total iron in ferroboron by potassium dichromate titrimetric method

After the sample was melted and decomposed by mixed flux of sodium hydroxide and sodium peroxide,the fusion sample was leached with hot water and acidized by 30 mL HNO3(1+1).Then sulfuric acid and phosphorus acid were added to eliminate nitrogen oxide and hydrogen peroxide.After the sample was further extracted by hydrochloric acid,stannous chloride was first added to reduce the majority of ferric iron into ferrous,then 7drops of 15g/L titanium trichloride solution was added until the solution turn blue in order to reduce the residue ferric iron into ferrous.Simultaneously,the impact of excess titanium trichloride was eliminated by the fading of tungsten blue oxidized by potassium dichromate.Finally,total iron in the sample solution was titrated by potassium dichromate standard titration solution with sodium diphenylamine as indicator to realize the determination of total iron in boron ferroalloy.Experiment indicated that the coexistence elements in ferroboron had no interference with the determination of total iron.The method was applied to determination of total iron in ferroboron certified reference materials.The results were conformed to the certified values,and the relative standard deviations(RSD,n=7)was smaller than 0.5%.