重铬酸钾滴定法测定铁钙包芯线中的铁

Determination of the Iron in Iron-calcium Cored Wire by Potassium Dichromate Titration Method

先用稀乙酸溶解试样中的钙粒,再用盐酸使还原铁粉溶解,在热的盐酸介质中,用SnCl2还原大部分的Fe3+为Fe2+,然后用TiCl3定量还原剩余的Fe3+,用钨酸钠做指示剂指示还原终点。在硫磷混酸存在下,以二苯胺磺酸钠为指示剂,用重铬酸钾标准溶液滴定铁量。测定结果满意,相对标准偏差≤0.207 1%(n=6)。

The calcium particles in iron-calcium cored wire sample were dissolved by dilute acetic acid and the reduced iron powder in the sample was dissolved further by hydrochloric acid. In the hot hydrochloric acid medium, the most Fe^2＋ was reduced to Fe^2＋ by SnCl2, and then the residual Fe^3＋ was reduced quantitatively by TiCl3, with sodium tungstate as indicator for reducing end. In the presence of sulfuric acid and phosphoric acid, making sodium diphenylamine sulfonate as indicator, the iron content was titrated by potassium dichromate standard solution. The satisfactory results were obtained and the relative standard deviation is less than 0.207 1% （n=6）.