三氯化钛-重铬酸钾滴定法测定炼钢尘灰中的TFe

Determination of TFe in Steelmaking Dust by Titanium Trichloride-Potassium Dichromate Titration

试样以硫磷混酸溶解后，加盐酸使铁转化为氯化铁，首先用SnCl2预还原大部分Fe3＋为Fe3＋然后用TiCI3定量还原剩余的Fe3＋为Fe2＋以钨酸钠作指示剂还原终点，即当Fe3＋定量还原为Fe2＋后，过量一滴TiCl3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，故溶液呈蓝色。过量的TiCl3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TiCl3还原剂的影响。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，相对标准偏差小于0．15％。

After the sample is dissolved by sulphur ＆ phosphorus mixed acid, the hydrochloric acid is added to transform ferric into ferric chloride, then SnCI2 is used to reduce most of Fe3 ＋ to Fe2 ＋ and the quantitative TiC13 is added to reduce surplus Fe3＋ to Fe2＋ ,taking sodium tungstate to indicate the reduction endpoint, that is,when all Fe3＋ is reduced to FeE＋ ,a excessive point of TiC13 solution is put into the solution, the colorless hexavalent tungsten in sodium tungstate will be reduced into the blue pentavalent tungsten compounds, so the solution color is blue. Under the catalysis of copper sulfate, the surplus TIC13 shall be oxidized by the dis- solved oxygen in water and the free oxygen in air to let the blue color of tungsten fade, thus, the influence of surplus TiCI~ reducer is eliminated. In the meditun of sulphur ＆ phosphorus mixed acid, with sodium dipheny- laminesulfonate as an indicator, the content of total ferric is titrated by potassium dichromate standard.solution and its relative standard deviation is less than 0. 15%.