EDTA差减滴定法测定钼精矿和钼焙砂中钼含量

摘要

Firstly, the reduction from molybdenum ( Ⅵ) to molybdenum ( Ⅴ ) by employing hydmxylamine 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.%用盐酸羟胺还原钼(Ⅵ)至钼(Ⅴ),EDTA络合钼(Ⅴ)及共存离子,锌盐滴定过量EDTA求得合量.于等量试液中不加盐酸羟胺,EDTA络合共存离子,滴定至近终点用酒石酸钾钠掩蔽钼(Ⅵ),锌盐滴定过量EDTA求得分量.二者之差即为钼量.2％ ～5％钨(Ⅵ)、铬(Ⅵ)或钒(Ⅴ)等共存离子不干扰测定.测定10.00 ～ 15.00 mg钼,相对误差-0.20％～ +0.20％,测定37％～57％的钼含量,相对标准偏差0.10％～0.15％,样品加标准回收率99.60％～ 100.80％.方法结果准确度与钼酸铅重量法的一致,但本法选择性好、分析快速.