微波消解-重铬酸钾滴定法测定稀土发火合金中铁含量

Determination of Iron in Rare Earth Pyrophoric Alloy by Microwave Digestion and Potassium Dichromate Titration

以盐酸作为消解试剂,采取高压密闭微波加热方法对稀土发火合金样品进行消解,加入氨水从而去除铜干扰,生成的沉淀加入盐酸溶解,加入二氯化锡三价铁还原,剩余的三价铁以钨酸钠为指示剂,加入三氯化钛进行还原。最后加入硫磷混酸,用重铬酸钾标准滴定溶液进行滴定,滴至二苯胺磺酸钠指示剂呈紫色,实现对稀土发火合金中铁量的测定。方法用于5个稀土发火合金样品中铁量的测定,相对标准偏差（n=11）均小于0.3%,回收率在99.6%-100.4%之间。本方法适用于稀土发火合金中铁含量的测定。

After the sample was dissolved by hydrochloric acid coupled with microwave digestion method at high pressure in a closed system,ammonium hydroxide solution was first added to reduce the interference of copper. The precipitate was then dissolved by hydrochloric acid. Stannous chloride was added to reduce majority of ferric iron,then titanium trichloride solution was added to reduce the residue ferric iron. Finally,iron was titrated by potassium dichromate standard titration solution with sodium diphenylamine as indicator for determination of iron in rare earth pyrophoric alloy. The method was applied for determination of five rare earth pyrophoric alloy samples,of which the relative standard deviations（RSD,n = 11） were smaller than0. 3%,and the standard addition recoveries were between 99. 6% and 100. 4%. This method is applicable to the determination of iron in rare earth pyrophoric alloy.