刚玉粉、高岭土、莫来石中铝、硅的测定

主要针对三种原材料中的Al含量和Si含量的分析方法进行讨论。采用容量法对其中的Al含量进行测定，在酸性溶液中，加入过量的EDTA溶液络合铝并掩蔽残余元素。在微酸性溶液中以二甲酚橙为指示剂，用氯化锌标准溶液滴定过量的EDTA，以氟化铵络合铝而游离出等量的EDTA。再用氯化锌标准溶液滴定至溶液呈橙红色即为终点。根据氯化锌标准溶液的消耗量换算出Al2O3的含量。采用重量法对其中Si含量进行测定，将熔融后的试样进行处理，使之生成硅酸沉淀。经灼烧、称重后以硫酸、氢氟酸进行挥硅处理，再灼烧称重，根据两次质量之差换算出SiO2的含量。两种分析方法均为经典化学分析方法，其分析结果准确可靠，并且具有广泛的使用性。

Quantitative Determination of Alumium and Silicon Elements in Corundum, Kaolin Clay and Mullite

Analytical methods for determination of Al and Si in three raw materials were discussed. Aluminum content was determined with volumetric method. Excess EDTA was added to acidic solution to form Al -EDTA complex and mask residue elements. In slightly acidic solution , the EDTA in excess was titrated with zinc chloride standard solution with xylenol orange as the indicator. Furthermore, the Al -EDTA complex was treated with ammonium fluoride and then the equal amount of EDTA was released into solution. The solution was titrated once more with zinc chloride standard solution and orange red color indicated the titration endpoint. The Al2O3 content was calculated by the volume of zinc chloride solution that was consumed. Gravimetric method was used to determine the silicon content. The melting sample was treated to form silicate precipitation. After incandesce and weighing, sulfuric acid and hydrofluoric acid were used for disposal of the silicon and then repeat incandesce and weighing. The content of SiO2 was determined according to the difference between the two weights. The two methods are both classic, accurate and reliable and can be widely used.