On the surface potentials of unimolecular films of long chain fatty acids. Part III.–The potentials of solid, liquid condensed and double layer films

Abstract
It was shown in Parts I and II that the vertical component of the mean molecular electric moment, μ¯, calculated with the aid of the Helmholtz equation 4 πn μ¯ = ∆V was dependent on the state of the film. Th experiments of Lyons and Rideal ( loc. cit. ) indicated that the state of a film could be altered not only by means of the usual variables, the two dimensional pressure F, and the temperature T, but also by the extent of the adhesion of the polar group to the substrate, conveniently altered in the case of acids by a change in the p H of the solution. That the change in this adhesion could not be attributed to the ionisation of the acid alone was shown by the fact that great changes in the stability of the film could be made over ranges of p H well outside the range of dissociation; further for identical hydrogen ion activities the effects of different anions possessing various capillary activities were widely diverse, e. g., the surface film on a citrate buffer behaves as if it were relatively more acid, and that on a borate buffer as if it were relatively more alkaline than the bulk phase.

This publication has 0 references indexed in Scilit: