Equilibrium spreading pressure of steroids

Equilibrium spreading pressure (ESP) for the three kinds of steroids, i.e., (I) 5-cholesten-3 beta-ol, (II) 5 alpha-chorestan-3 beta-ol, and (III) 5 b eta-cholestan-3 alpha-ol, was measured as a function of temperature and dis cussed thermodynamically in connection with their pi-A relationships and th e thermal results such as the melting point and the heat of fusion. It beca me clear that the direction of the OH moiety positioned at the 3rd-carbon a tom of the steroid molecule gives a considerably large effect on the variou s thermodynamic properties in the solid states or in the monolayers an the water surface.