Complex Formation Between Alkaline Earth Cations and 4-(2-Pyridylazo)Resorcinol in Ethanol-Water Mixtures

Abstract
The interaction between alkaline earth cations and 4-(2-pyridylazo)resorcinol in C2H5OH-H2O mixtures has been studied spectrophotometrically. Formation constants for the resulting 1:1 complexes with different amounts of water in ethanol were determined. There is an inverse relationship between the complex formation constant and amount of water in the mixed solvent. In all solvent mixtures used, the stability of the complexes was found to vary in the order Mg2 + > Ca2+ > Sr2+ > Ba2 +. A linear relationship is observed between log Kt for complexes and the mole fraction of ethanol.