三氯化钛还原-重铬酸钾滴定法测定球团矿中全铁的改进

Titanium trichloride reduction -- Potassium dichromate titration method for the determination of pellet in the improvement of TFe

由于球团矿中全铁的测定，日常习惯套用文献，以硫磷混酸溶解试样的重铬酸钾滴定法，测定Tfe结果普遍偏低。为此，本文改用碱混合熔剂熔融试样代替硫磷混酸冒烟溶解试样，熔融物以热水浸取盐酸酸化后。首先用氯化亚锡将大部分Fe3＋还原成Fe2＋；然后用TiCl3还原剩余的Fe3＋，以钨酸钠做指示剂指示还原终点，即当Fe3＋定量还原为Fe2＋后，过量一滴TiCl3溶液，可使作为指示剂的六价钨（无色）还原成蓝色的五价钨化合物，俗称“钨蓝”，故溶液呈蓝色。过量的TiCl3可在硫酸铜的催化下，借水中的溶解氧和空气中的游离氧氧化使钨蓝色泽褪去，从而消除过量的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，分析结果令人满意。该法测定全铁的绝对误差小于0．15％，避免了用重铬酸钾氧化褪去钨蓝色泽时易引入的误差。

Because of pellet - Determination of TFe, daily habits in literature , with a mixture of sulfuric acid and phosphoric acid to dissolve the sample by potassium dichromate titration method for determination of TFe results, generally low. Therefore, this paper use mixed alkali flux melting sample replacing the mixture of sulfuric acid and phosphoric acid to dissolve the sample to smoke, the melt water leaching in hydrochloric acid acidizing, first by using stannous chloride will most Fe3＋ back into Fe2＋; and then use the TiCl3 reduction of residual Fe3＋, with sodium tungstate as indicator indicator reduction destination, i.e. when the quantitative reduction of Fe3＋ to Fe2＋, excess a drop solution TICl3, can make as an indicator of six valence tungsten （ colorless ） reduction into blue tungstic compounds, commonly known as ＂ tungsten blue ＂, so the solution is blue. Overexpression of TiCl3 in copper sulfate catalyst, by dissolved oxygen and air free oxygen in the tungsten oxide blue color fading, thus eliminating excessive TiCl3 effect of reducing agent. In the mixture of sulfuric acid and phosphoric acid medium, with two aniline sulfonic acid sodium as indicator, with titration of potassium dichromate standard solution TFe, the result of analysis is satisfactory. The method of determination of TFe absolute error is less than 0.15%, avoids the use of potassium dichromate oxidation fading tungsten blue Ze Yi errors.