The sorption of vapours by ferric oxide gel. I.―Aliphatic alcohols

Abstract

In this paper isothermals of a series of alcohols on ferric oxide gel at 25°C are described. The sorption of methyl, ethyl, n. and iso-propyl, and n. butyl alcohols has been investigated in order to determine how the nature of the isothermal alters with the size of the adsorbed molecule. Isothermals of benzene and ethyl alcohol on ferric oxide gel have been described previously, and an examination of these data leads to the conclusion that the hysteresis phenomena are associated with a capillary condensation process which follows a true adsorption process on the surface of the pores. The application of the Kelvin equation to the calculation of the capillary radii at corresponding volumes gives the values 16 and 18 A respectively, from the benzene and alcohol isothermals. The lack of complete agreement may, of course, be due to the fact that the limit of validity of the equation has been reached, but there remains a possibility that the difference actually arises from the variation in the thickness of the adsorbed layer with the size of the adsorbed molecules. A similar conclusion was arrived at from an examination of the isothermals of methyl and ethyl alcohol on a specimen of silica gel which exhibits hysteresis, and the present series has therefore been determined in order to provide more extensive data for testing the validity of the Kelvin equation.