黄钠铁矾中铁的测定

Determination of Iron in Sodium Jarosite

准确快速测定黄钠铁矾中铁的含量有利于控制铁湿法冶金的流程。采用氢氧化钠溶液分解试样,盐酸(1+9)溶解滤渣,蒸发除过量酸,氨水沉淀分离铜、镍、钴等元素,再用稀盐酸溶解沉淀。在盐酸介质中,SnCl_2将大部分Fe(Ⅲ)还原为Fe(Ⅱ),钨酸钠为指示剂,用TiCl_3还原呈钨蓝色,重铬酸钾滴定至蓝色褪去。再以二苯胺磺酸钠为指示剂,重铬酸钾标准溶液滴定测定样品中铁的含量。实验表明,黄钠铁矾中共存干扰元素绝大部分被分离,同时与酸溶解法进行比较,测定数据一致,相对标准偏差(n=9)小于0.1%。

Rapid and accurate determination of iron content is conducive to control iron hydrometallurgical processes. In this paper, the sodium jarosite sample was decomposed by sodium hydroxide solution, and the residue was dissolved in a 10% hydrochloric acid medium. Excess acid was removed by evaporation. Ammonia was used to separate copper, nickel, cobalt and other elements from precipitation of iron hydroxide, and then the precipitation was dissolved in hydrochloric acid. In hydrochloric acid medium, a large amount of Fe （Ⅲ） is reduced to Fe （Ⅱ） by SnCl2. Choosing sodium tungstate as an indicator, the solution titanium trichloride was added until the solution turned blue. Then, the potassium dichromate solution was added to oxidize the excess of titanium （Ⅲ） until the solution became colorless. Total iron contents were determined by titration with potassium dichromate standard solution by using diphenylamine sulfonate as an indicator. The results showed that most of coexisting elements in the sodium jarosite were separated. The values determined by this method were consistent with those by acid separation. The relative standard deviation （RSD, n=9） was less than 0.1%.