Measuring iron content in iron ore by titrimetric analysis

In SnCl2-TiCl3-K2Cr2O7 titrimetric analysis,the iron ore was thermally decomposed under hydrochloric acid plus sodium fluoride,so that iron oxides and silicates had become iron oxide into the solution.First of all,ferric ions was reduced to ferrous iron by the stannous chloride,other ferric iron was reduced to ferrous iron by titanium trichloride to generate tungsten with sodium tungstate as the indicator.Next,the solution was titrated by potassium dichromate standard solution until the blue was disappeared.After adding mixed acid,the solution was titrated by potassium dichromate standard solution with diphenylamine sulfonante as indicator.The experimental conditions were optimized through improving the reduction acidity,reduction temperature,time of dissolved sample and reagent dosage.The relative standard deviation was in the range of 0.68%～2.6%,and the recovery rate was in the range of 91.9%～97.9%.The results show that the method is accurate and reliable.