Effect of addition agents on the syneresis of sodium oleate gels in pinene

Abstract

The effect of a number of addition agents on the syneretic phenomenon exhibited by gels of sodium oleate in pinene has been investigated. The addition agents employed are sodium stearate, sodium palmitate, potassium stearate, oleic acid, stearic acid, palmitic acid, benzene, toluene, xylene, mesitylene, aniline, phenylene diamine and nujol. The soaps retard and tend to stop the syneretic phenomenon, the retarding effect being in the order of NaP > KSt > NaSt. The effects of the three closely related fatty acids on the syneretic phenomenon are totally different from one another. Benzene and toluene retard the syneretic process but xylene and mesitylene accelerate it. There appears to exist an approximately linear relationship between the percentage retardation or acceleration for the same amount of benzene, toluene, xylene and mesitylene, and the number of -CH₃ groups contained in these substances. No such relationship can be observed in the case of amino compounds among which benzene retards and aniline and phenylene diamine accelerate the syneretic process. The retarding effect of nujol, a heavy paraffin oil, on the syneretic process is analogous to that of either of the soaps used in this investigation inasmuch as syneresis is retarded and there is a tendency to stop it altogether. An attempt has been made to explain the various behaviour on theoretical considerations.