The structure of thin films. Part XII.—Cholesterol and its effect in admixture with other substances

In 1923, Leathes showed that cholesterol, when mixed with certain fatty acids in monomolecular films on water or dilute hydrochloric acid, caused a diminution of the area occupied by the fatty acids. Under conditions when the acid, if present alone in the film, would be an expanded film, in the presence of fairly small amounts of cholesterol, the film was found to have the area of a condensed film. This paper gives a further analysis of this action of cholesterol. The only means which appear available for attack on the problem, are (a ) the examination of mixtures of cholesterol with suitable substances forming expanded films, measuring the degree to which the area is reduced by various proportions of cholesterol; (b ) the comparison of the action of cholesterol with that of other substances which might be expected to have a similar effect.