铁的氧化还原法由于准确、快速且适应范围广,至今仍在广泛应用。而用铬盐滴定灵敏度较低,当标准溶液浓度低于0.015N时,用二苯胺磺酸钠指示剂变色不明显。为适应硅酸盐元素系统分析时取样较少的需要,选择铈盐容量法滴定,即使浓度比上述铬盐再降低十倍,也可观察到清晰的终点变化。本文在无汞铬盐测定铁的基础上,进一步试验了以硫酸铈标准溶液氧化滴定法测定硅酸盐中铁,并以钨酸钠,乙基橙做为钛盐还原铁的指示剂,以铜盐催化氧化消除多余还原剂产生的少量“钨蓝”。对比选择了铁的氧化还原指示剂邻氨基苯甲酸,亚铁—隣菲啰啉,二苯胺磺酸钠等,以后者最佳。在 Iron oxide redox method is still widely used due to its accuracy, rapidity and wide adaptability. The use of chromium salt titration lower sensitivity, when the standard solution concentration is less than 0.015N, with sodium diphenylamine sulfonate indicator discoloration is not obvious. In order to meet the needs of less sampling during silicate elemental system analysis, cerium volumetric titration was selected and a clear end point change was observed even at concentrations ten times lower than the chromium salts described above. In this paper, mercury-free chromium salt determination of iron on the basis of further tests with cerium sulfate standard solution of titrimetric determination of iron in silicate, and sodium tungstate, ethyl orange as a titanium salt reduced iron indicator, copper Salt oxidation catalyzes the elimination of a small amount of “tungsten blue” produced by excess reductants. Contrast selected iron redox indicator anthranilic acid, ferrous - phenanthroline, diphenylamine sulfonate, the latter best. in