我国稀土资源极其丰富,是世界储量和品种最多的国家。随着含稀土的钢铁及有色合金品种的逐渐增多,因而寻找灵敏度高,选择性好的显色剂,扩大光度分析的应用范围是广大分析工作者极为关注的问题。对于微量稀土元素的光度测定,国内外曾作过不少工作,也提出过多种类型的有机显色剂。应该指出,近十几年来变色酸双偶氮衍生物为新掘起的、很有前途的显色剂。在实践中以变色酸双偶氮衍生物比单偶氮衍生物更有价值,应用更广。例如偶氮氯膦-Ⅲ,由于具有较强的成盐基团膦酸基(-PO_3H_2),并在偶氮基对位上引入一个Cl原子,因而形成的络合物更 Our country is extremely rich in rare earth resources, is the world’s reserves and varieties of the most countries. With the gradual increase of varieties of rare earth-containing steel and non-ferrous alloys, it is a matter of great concern to the analysts to expand the application of photometric analysis to find a developer with high sensitivity and good selectivity. For the determination of trace rare earth elements photometry, both at home and abroad have done a lot of work, but also proposed a variety of types of organic developers. It should be pointed out that the chromotropic acid disazo derivatives have been newly emerging and very promising developers in recent ten years. In practice, the chromotropic acid disazo derivatives are more valuable than monoazo derivatives and are more widely used. For example, chlorophosphonazo-III, which has a stronger salt-forming group phosphonic acid group (-PO 3 H 2) and a Cl atom on the para-azo group,