The Influence of a Simple Electrolyte KCI on Surfactant - Dye Interactions in Water Solution

Abstract

The influence of a simple electrolyte KCI on the interactions between the anionic dyes C. I. Acid Orange 7 (AO7) and the cationic surfactant N-cetylpyridinium chloride (CPCl) in water solutions was studied. To determine the equilibrium association constants, which enabled us to make the conclusions about the strength of interactions the Method of Continuous Variations was used. The light absorption of mixed dye and surfactant solutions in the visible absorption range at 25°C was measured. The concentration of the dye in the measured solutions was up to 6· 10−5 mol-1−1 and the concentration of the surfactant was up to 1.2· 10−4 mol· 1−1, which is below the critical micelle concentration of surfactant in pure water. The molal concentrations of KCl in the measured solutions were 0, 0.1, 0.5 and 1 mol/kg. It was found that the addition of KCI reduces the tendency of the dye AO7 and the surfactant CPC1 to associate.