三氯化铁分解重铬酸钾滴定法测定直接还原铁中金属铁

Determination of metallic iron in direct reduced iron by potassium dichromate titration after decomposition of sample by ferric chloride

试样用三氯化铁溶液溶解，金属铁被氧化为二氯化铁，过滤分离，滤液酸化后以二苯铵磺酸钠为指示剂，用重铬酸钾标准溶液滴定。确定了试样粒度在0．125mm以下、三氯化铁溶液浓度和用量分别为100g／L和40mL、搅拌时间为30min的最佳实验条件。用本法测定直接还原铁样品，相对标准偏差小于2％，加标回收率在99．5％～101．2％之间。

The sample was dissolved in ferric chloride solution to oxidize metallic iron into ferrous chloride. With sodium diphenylamine sulfonate as indicator, the obtained solution was titrated with potassium dichromate standard solution. The optimum conditions were obtained ： sample size was below 0. 125 mm; volume of 100 g/L ferric chloride solution was 40 mL;stirring time was 30 min. In the application of this method to determine direct reduced irons, the RSD was less than 2 % and the recovery was 99.5%--101.2%.