The effect of added salts in water on the hydrophile-lipophile balance of nonionic surfactants: The effect of added salts on the phase inversion temperature of emulsions

Abstract

Abstract Although an HLB-value is assigned to a definite surfactant, the real hydrophile-lipophile balance (HLB) of surfactant at the oil-water interface changes with the amount and kinds of added salts in water as well as with the types of oils. On the other hand, the phase inversion temperature (PIT) of emulsions accurately reflects that the real HLB of surfactant in a given system changes sensitively with the amount and kinds of added salts. The effect of added salts, acid, and alkali on the hydrophile-lipophile balance of nonionic surfactant has been studied from the measurement of the effect of these additives on the PIT of emulsions and on the cloud points of the surfactant solutions. It was found, for example, that both the PIT of the emulsions studied and the cloud point of an aqueous solution of polyoxyethylene (9.7) nonylphenylether (5 wt % per system) were depressed about 14°C in the presence of 6 wt % of sodium chloride in water. This means that the HLB value of the surfactant was depressed about 0.8–1.0 unit in the solution.