本文研究了稀土元素和偶氮氯膦-m-SO_3H的络合反应。提出了这类络合物只存在α型反应和不形成β型络合物。测定了试剂和稀土元素络合物在水溶液和在50％水-乙醇溶液中的络合比均为RE:R=1:2,并指出络合物的α吸收峰的峰高随着溶液中乙醇、丙酮等含量的增加而升高。根据稀土元素和试剂的络合物的性能,提出了不经分离Fe~卌,用草酸掩蔽Fe~卌,在50％的水-乙醇溶液中,以直接光度法测定球铁中微量稀土总量的方法。 In this paper, the complexation of rare earth elements with chlorophosphonazo-m-SO 3 H 3 was studied. It is proposed that such complexes only have α-type reactions and do not form β-type complexes. The complexing ratio of the reagent to the rare earth element complex in an aqueous solution and in a 50% water-ethanol solution was determined to be RE: R = 1: 2, and it was indicated that the peak height of the alpha absorption peak of the complex increased with increasing Ethanol, acetone and other content increases. According to the properties of complexes of rare earth elements and reagents, it is proposed to determine the total amount of trace rare earths in the ductile iron by direct photometry in a 50% water-ethanol solution without the separation of Fe ~ Methods.