硫酸铜催化代替氯化汞氧化重铬酸钾滴定法测定铁矿石中TFe

试样以硫磷混酸溶解后,加盐酸使铁转化为氯化铁,首先用SnCl_2预还原大部分Fe~(3+)为Fe~(2+),然后用TiCl。定量还原剩余的Fe~(3+)为Fe~(2+),以钨酸钠作指示剂还原终点,即当Fe3+定量还原为Fe~(2+)后,过量一滴TiCl_3溶液时,可使作为指示剂的钨酸钠中的六价钨(无色)还原成蓝色的五价钨化合物,故溶液呈显蓝色。过量的TiCl_3可在硫酸铜的催化下,借水中溶解氧及空气中的游离氧氧化使钨蓝色泽褪去,从而消除过量TiCl_3还原剂的影响。避免了国标法及经典法的无汞测铁分析方法用重铬酸钾氧化过量TiCl_3时易引入的误差。在硫磷混酸介质中,以二苯胺磺酸钠为指示剂,用重铬酸钾标准溶液滴定全铁量,取得了令人满意的结果。

Determination of TFE in iron ore instead of with copper sulfate suifate as catalyst potassium dichromate titrimetric method

With the sample dissolved with Sulfuric-phosphoric mixed acid,SnCl2 was used to pre-deoxi-dize the most of Fe3＋ into Fe2＋.Then with sodium tungstate as an indicator,TiCl3 was used to quantita-tively reduce the remaining Fe3＋ to Fe2＋,and the exces TiCl3 could be oxidized by the oxygen dissolved in solution and free oxygen in air,under the catalyzing of copper sulfate, making its tungsten-blue luster fade,to eliminate the effect of the superfluous reducing agent TICl3, thus avoiding errors liable to induc-ting when potassium dichromate was used to oxidize superfluous TiCl3 in the mercury-free iron-determina-tion analytical methods in the State Stsndards and Classic Methods.In medium of sulfur-phosphor mixed acid,with diphenylamine-sodiun-sulfonic acid as an indicator,the standard solution of potassium dichro-mate was used to titrate the total iron content,the result being satisfactory.