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提出了用三氯化铁分解试样、重铬酸钾滴定法测定亚铁的分析方法.试样用三氯化铁溶液溶解,金属铁被氧化为二氯化铁进入溶液,亚铁留在沉淀中,过滤、分离,在隔绝空气的条件下,以盐酸和氟化钾溶液溶解沉淀,二苯铵磺酸钠为指示剂,用重铬酸钾标准溶液滴定.本文对方法中试剂浓度、用量、时间、滴定介质、干扰元素等影响因素进行试验,确定了三氯化铁溶液浓度和用量为100 g/L和30 mL、搅拌时间为20 min的最佳实验条件.该法测定直接还原铁中亚铁,相对标准偏差小于2%,加标回收率在98%～101%之间.

A determination method of iron(Ⅱ) in direct reduced iron was developed by iron trichloride decomposi-tion-potassium dichromate titration. The sample was dissolved in irom trichloride solution. The metallic iron in sample was oxidized to ferrous chloride before entering into solution, while the iron(Ⅱ) remained in the sediment, which then was filtered and separated. In vacuum, the sediment was dissolved by hydrochloric acid and potassium fluoride. The solution was titrated with potassium dichromate standard solution with sodium diphenylamine sulfonate as indicator. The effects of concentration and dosage of reagent, time, titration medium and interference elements were investigated. The optimal experimental conditions were obtained: the concentration and dosage of iron trichloride were 100 g/L and 30 mL, and the stirring time was 20 min. This method was applied to the determination of iron(Ⅱ) in direct reduced iron, with the relative standard deviations (RSD) of less than 2 % and the recoveries in the range of 98 %-101%.