硅酸盐矿物中二氧化硅含量较高,通常采用重量法测定,近来采用氟硅酸钾容量法测定的日益增多。当用重量法时,有用盐酸-氯化铵脱水;或用动物胶、溴化十六烷基三甲铵(CTMAB)、聚环氧乙烷(Peo)等作为凝聚剂,使硅沉淀。据资料介绍,以 CTMAB为凝聚剂的沉淀回收率≥99%,而我们试验结果,滤液中仍残留约2毫克硅,且滤液需破坏 CTMAB 后才能用比色法测定,手续繁杂。我们采用了已推荐作为标准方法的 Peo 凝聚剂重量法,并以钼蓝光度法补偿测定硅,结果准确,省时,金属离子不水解,而且滤 Silicate minerals in the silica content is higher, usually by gravimetric method, the recent determination of potassium fluosilicate volume method is increasing. When using gravimetric method, the use of hydrochloric acid - ammonium chloride dehydration; or animal glue, cetyl trimethyl ammonium bromide (CTMAB), polyethylene oxide (Peo), etc. as a coagulant, the precipitation of silicon. According to the information, with CTMAB coagulant precipitation recovery of ≥ 99%, and our test results, the filtrate remained about 2 mg of silicon, and the filtrate to be destroyed after CTMAB colorimetric determination, complicated procedures. We have adopted the Peo coagulant gravimetric method, which has been recommended as the standard method, and the silicon is compensated for with the molybdenum blue photometry method. The result is accurate, time-saving and the metal ions are not hydrolyzed,