Abstract
The equilibrium surface tension of the aqueous solution of aliphatic alcohol and sulfonated dye mixture was measured as a function of the total molarity and mole fraction of dye of the mixture under atmospheric pressure at 298. 15 K. The systems used were n-butanol (BuOH) and C. I. Direct Red 39 (DR-39), and n-pentanol (PeOH) and C. I. Acid Orange 7 (AO-7) mixtures. In the former, the surface-activity of the alcohol was lower than that of the mixed dye, but in the latter, that of the alcohol was higher. By applying Motomura's thermodynamic equation, the total surface density and composition of the mixed adsorbed film were evaluated numerically. In the BuOH and DR-39 mixture system, the mixed adsorbed film abounded in DR-39 over the whole composition range of solution, while in the PeOH and AO-7 mixture system, the mixed adsorbed film abounded in PeOH. The same phenomena were recognized for the benzyl alcohol and acid dye mixture system. These results showed that the composition of the mixed adsorbed film was predominant in the more surface-active component.
