Determination of Molybdenum Content in Molybdenum Concentrates and Molybdenum Calcine by EDTA Difference Titration

Firstly,the reduction from molybdenum(Ⅵ) to molybdenum(Ⅴ) by employing hydroxylamine hydrochloride,and complexation of molybdenum(Ⅴ) and co-existent ions by EDTA were conducted,and then the resultant was obtained by titrating excessive EDTA with zinc salt.Secondly,based on complexation of co-existent ions without hydroxylamine hydrochloride in equivalent test solution,molybdenum(Ⅵ) was masked with potassium sodium tartrate at the titration end-point,after that,the component was got by titrating excessive EDTA with zinc salt.The difference of the resultant and the component was molybdenum content.The determination was not interfered by coexistent ions of tungsten(Ⅵ) with more than 2%~5% content,chromium(Ⅵ) or vanadium(Ⅴ).For determining 10.00~15.00 mg molybdenum and molybdenum with 37%~57% content,the relative error and the relative standard deviation were-0.20%~+0.20% and 0.10%~0.15%,respectively.The standard recovery of samples was 99.60%~100.80%.The result accuracy of the proposed method was consistent with that of lead molybdate gravimetry,but it was of good selectivity and rapid determination.