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弗里兹(J.S.Fritz)和弗里伦德(M.Q.Freeland)建议用茜素红S及钍试剂(APANS)为指示剂来测定常量和微量的硫酸盐。方法是在pH=3～3.5下,用钡盐标准溶液直接滴定硫酸盐30～40%(V/V)乙醇溶液的快速容量法,终点明显,操作简便,为现有文献报导测定硫酸盐最快速的方法之一。但用于测定碱金属的硫酸盐时,与重量法一样也遇到了共沉淀和表面吸附作用的影响,误差很大。故不得不采用离子交换法以除去碱金属离子的干扰。因此必须增加过滤、洗滌等操作,这样不仅使手续烦杂及延长测定时间,同时又要增加仪器设备。作者以茜素红S为指示剂,用氯化钡直接测定硫酸钠,找到了最合适的测定条件。并采用醋酸调节酸
J.S. Fritz and M.Q. Freeland propose that alizarin red S and thorium reagents (APANS) be used as indicators to determine the presence and absence of traces of sulfate. The method comprises the following steps: directly titrating the rapid volumetric method of using 30 to 40% (v / v) sulfate ethanol solution with barium salt standard solution at pH = 3 to 3.5, the end point is obvious, and the operation is simple and convenient, One of the quick ways. But for the determination of alkali metal sulfate, the same as the gravimetric method also encountered the effect of coprecipitation and surface adsorption, the error is very large. So I have to use ion exchange method to remove the interference of alkali metal ions. Therefore, we must increase the filtering, washing and other operations, so that not only complicate procedures and extend the measurement time, but also increase the equipment. With Alizarin red S as indicator, sodium alginate was directly determined by barium chloride, and the most suitable determination conditions were found. Acetic acid and adjust the acid