Studies on beta-type reaction and kinetics of lanthanides with p -bromochloroarsenazo

摘要

The reaction behaviour of the beta-type chelates of lanthanide ions (Ln~(3+)) with p -bromochloroarsenazo (4-CAsA-pB) in 0.01 mol l~(-1) HC1O_4 solution has been studied systematically by a spectrophotometric method. All the Ianthanide ions can form beta-type chelates with beta-bromochloroarsenazo. The maximum absorption wavelength is in the range 727-731 nm, the molar absorptivities are about 6 0 × 10~4-9.0 × 10~4cm~2 mol~(-1), the composition ratio of Ln~(3+) ions with 4-CAsA-pB is 1:2 and the actual combining ratio is 2:4. The optimum acidity range (ApH value) of the formation of beta-type chelates has been obtained. Kinetic parameters, such as the reaction order and rate constants, have also been studied and a formation mechanism for the beta-type chelates has been proposed.