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本文用光度法研究了4-(2-噻唑偶氮)-间苯二酚(TAR)的酸碱平衡及TAR与Cd(Ⅱ)的配合反应。用图解法和MINISPEF程序计算得到TAR的逐级离解常数(pKa_1=0.099,pKa_2=6.24,pKa_3=9.64),确定TAR与Cd(Ⅱ)的体系中,存在MHR、MR、MR_2三种配合物。MHR、MR、MR_2的最大吸收波长分别在510nm、505nm、530nm,稳定常数分别是,1gβMHR=13.40,1gβMR=7.19,1gβMR_2=11.39。本文还给出了测定微量Cd(Ⅱ)的分光光度方法。
In this paper, the acid-base equilibria of 4- (2-thiazolylazo) -resorcinol (TAR) and the complexation of TAR with Cd (Ⅱ) were studied spectrophotometrically. The dissociation constants of TAR (pKa_1 = 0.099, pKa_2 = 6.24, pKa_3 = 9.64) were calculated by the graphic method and the MINISPEF program. Three complexes of MHR, MR and MR_2 were identified in the systems of TAR and Cd (Ⅱ). The maximum absorption wavelengths of MHR, MR and MR_2 are 510nm, 505nm and 530nm, respectively. The stability constants are 1gβMHR = 13.40, 1gβMR = 7.19 and 1gβMR_2 = 11.39, respectively. This article also gives a spectrophotometric method for the determination of trace Cd (Ⅱ).