Studies on the β-type Chromegenic Reaction of Lanthanides with p-Bromochloroarsenazo

摘要

The reaction behavior of the β-type chelates of lanthanide ions (Ln~(3+)) with p-bro-mochloroarsenazo (4-CAsA-pB) in 0. 01 mol. 1~(-3)HClO_4 solution have been systematically studied by spectrophotometric method. All of the lanthanide ions can form β-type chelate with p-bro-mochloroarsenazo, maximum absorption wavelength in the range of 727-731 nm, mole absorp-tivities being about 6. 0×10~4 -9.0×10~4 cm~2 mol~(-1), composition ratio of Ln~(3+) with 4-CAsA-pB to be 1: 2 and the actual combining ratio being 2 :4. The optimum acidity range (ApH value) of forming β-type chelates have been obtained. The kinetic behavior, such as reaction order, rate constants have also been studied and a mechanism of forming β-type chelates has been proposed.