Open AccessThe structure of surface films. Part XVIII. ─The effect of alkalinity in the underlying solution on films of fatty acids
Author(s) -
N. K. Adam,
J. G. F. Miller
Publication year - 1933
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1933.0177
Subject(s) - alkalinity , dissociation (chemistry) , molecule , electrolyte , chemistry , aqueous solution , adhesion , chemical engineering , inorganic chemistry , organic chemistry , electrode , engineering
Historical . It has been known for some time that extensive changes occur in monomolecular films of fatty acids on aqueous solutions, as the alkalinity or acidity is varied. These changes are of at least tow kinds; changes in the packing of the molecules in the coherent types of film, and changes in the lateral adhesion between molecules have already been described. Thus Adam found changes in the packing of the molecules in the condensed films on changing from neutral to acid solution; and also a change from condensed to gaseous or vapour expanded films, on changing from natural to strongly alkaline solutions. The second of those effects was considered to be due to a decrease in the lateral adhesion between the molecules, caused by the development of similar electric charges on the end groups, through electrolytic dissociation of the carboxyl group on alkaline solutions. On alkaline solutions, it has previously been noted that the films contract spontaneously; Adam called this "solution," but did not examine it in detail; Lyons and Rideal believed it to be not a complete solution, but the formation of a bimolecular layertwo molecules thick; Zocher and Stiebel, by ultramicroscopic examintion, concluded that this disappearance of the film was due to a partial collapse into thick, localized aggregates, not into a uniform bimolecular film.