随着原子能事业的发展，接触钍的人员相应增加，建立尿钍的测定方法对于辐射防护监测，保障工作人员健康，具有一定意义。

我们采用磷酸铋共沉淀法测定人尿中的钍，可测限度为0.2µg，与文献〔1〕一致，可适用于厂矿工作人员的健康调查。

Bismuth nitrate and phosphonic acid produce co-precipitation of bismuth phosphatethorium in 0.2

M

nitric acid system. The developing reaction of thorium to arsenazo III is determined by colorimetry. Sodium hexameta-phosphate is used to break up the developing chelating structure between arsenazo III and thorium so as to minimize the interference in measurement. The measurable limit of this method is 0.2µg. When 0.2µg thorium is added to the urine

its recovery rate is around 90%

with±10%relative error.