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在浓磷酸介质中,加入过量亚铁将六价钼还原为五价钼,再用重铬酸钾溶液电位滴定或光电比色滴定高含量钼的方法已有报道。本文在前人工作的基础上,参考盐酸氯丙嗪(Chlorp romazine hyarochloride)在酸性介质中能被多种氧化物氧化成红色化合物的性质,以其作为指示剂,在进一步提高磷酸酸度,并以抗坏血酸还原掩蔽高价铬、锰、铈等金属离子的条件下,改用亚铁直接滴定钼(Ⅵ),终点由红色转蓝色很明显。方法已成功地应用于钼铁、钼精矿以及选、冶中间产品的日常分析,经受了生产实践的检验。试样溶解后,可不经任何分离手续直接滴定。方法简单快速、成本低、再现性好,与重量法对照结果吻合。主要试剂钼标准溶液:1毫升含1毫克钼,硫酸亚铁铵标准溶液:约0.035mol/L的5％硫酸溶液,标定滴定度;盐酸氯丙嗪指示剂:0.5％水溶液,贮于棕色瓶中。
In concentrated phosphoric acid medium, excessive ferrous iron is added to reduce hexavalent molybdenum to pentavalent molybdenum, then potassium dichromate solution potentiometric titration or photoelectric colorimetric titration high content of molybdenum has been reported. Based on the previous work, this paper refers to the property that chlorp romazine hyarochloride can be oxidized by many oxides into red compounds in acid medium. Using it as an indicator, the acidity of phosphoric acid is further improved and the Ascorbic acid reduction masking high prices of chromium, manganese, cerium and other metal ions under the conditions of direct titration with ferrous molybdenum (Ⅵ), the end point from red to blue is obvious. The method has been successfully applied to the daily analysis of ferro molybdenum and molybdenum concentrates, as well as the selection and smelting intermediates, which have undergone the test of production practice. After the sample is dissolved, it can be directly titrated without any separation procedures. The method is simple, rapid, low cost, good reproducibility, consistent with the weight method control results. The main reagent molybdenum standard solution: 1 ml containing 1 mg of molybdenum, ammonium ferrous sulfate standard solution: about 0.035mol / L of 5% sulfuric acid solution, calibration titer; chlorpromazine hydrochloride indicator: 0.5% aqueous solution, stored in a brown bottle in.