Stability of emulsions of water in oil. I. The correlation between electrokinetic potential and stability

Abstract

Experiments on W/O emulsions of moderate concentration, stabilized with oil-soluble, ionizing stabilizers, show that in these emulsions no correlation exists between stability against flocculation and electrokinetic potential. Although, according to theoretical calculations, energy barriers of over 15 kT are present, if the radius of the dispersed globules is about 1 μ and the electrokinetic potential exceeds 25 mv., they apparently do not prevent lasting contact between particles. All our emulsions flocculate rapidly, even in the presence of a surface potential considerably higher than 25 mv.

A rather pronounced anticorrelation exists between the zeta potential and coalescence. It is explained as a consequence of the free mobility of the stabilizing molecules in the interface.

The good stabilization against coalescence caused by some oleates of polyvalent metals is due to the formation of a thick film of partial hydrolyzates in the interface.