The Influence of the Cationic Surfactant on the Coloration of Chromogenic Reagents (). The Dissociation Constants of Sulfophthalein Indicators in the Presence of Zephiramine

[摘要] The absorption spectra and the dissociation constants of various sulfophthaleins have been measured in the presence of a cationic surfactant. In the presence of 2.0 ¡¿ 10-3 M zephiramine and an ionic strength of 0.05 at 25¡¾1¡É the absorption maxima of the basic forms are shifted to red by 6¡­21 nm and their molar absorptivities are increased, while the absorption maxima of the yellow forms are shifted to blue by 4¡­20 nm and their molar absorptivities are decreased. The decreases in pKa values are of the order of ranging -1.38¡­0.37. The characteristic of the observed changes has been explained by the assumption that the dye molecule adsorbed on micellar surface forms a stable coplanar structure easily and then the conjugation in the dye molecule is elevated.

[学科分类] 化学（综合）