对于微量希土元素的光度测定,国内外曾作过不少工作,也提出过多种类型的有机显色剂。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。应该指出,近十几年来变色酸偶氮衍生物为新崛起的很有前途的显色剂。通过实践知道变色酸的双偶氮衍生物比其单偶氮衍生物尤有价值。而在变色酸双偶氮型显色剂与希土元素的络合反应中,β-型显色反应与α-型显色反应相比,往往显现出对比度大、灵敏度高和选择性好等特 For trace amount of rare earth element photometry, both at home and abroad have done a lot of work, but also proposed a variety of types of organic chromogenic agents. Looking for high sensitivity and good selectivity of the developer, expanding the scope of application of photometric analysis is the majority of analysts are extremely concerned about the problem. It should be pointed out that the chromotropic acid azo derivatives have been promising new color developing agents in recent ten years. It is known by practice that bis-azo derivatives of the chromotropic acid are more valuable than their mono-azo derivatives. In the complexation reaction of chromogenic acid disazo type developer with rare earth element, the β-type color reaction tends to show high contrast, high sensitivity and selectivity compared with the α-type color reaction special