通常是以锌、镁、钍或铋的正磷酸盐沉淀出来,然后再将沉淀溶解,以 EDTA 溶液滴定金属离子的容量分析方法测定磷。这些方法,以及惯用的以磷钼酸盐沉淀滴定的方法,总因为在最终分析以前必须进行磷酸盐的沉淀、过滤与重新溶解商显得不便。磷酸盐的测定,几乎无有效的直接滴定法,对于微量的磷酸盐的测定尤其是这样。 Usually zinc, magnesium, thorium or bismuth orthophosphate precipitation, and then the precipitate was dissolved in EDTA solution titration of metal ions volumetric determination of phosphorus. These methods, as well as the customary methods of titration with phosphomolybdate precipitation, are often inconvenient because of the need for phosphate precipitation, filtration and resolubilization before the final analysis. There is almost no direct titration of phosphates, especially for the determination of trace phosphates.