HEATS OF WETTING OF POROUS BODIES BY WATER AND METHYL ALCOHOL

Heats of wetting by water and methyl alcohol were determined in the case of three samples of charcoal, a sample of bentonite and a sample each of silica, alumina, ferric oxide and chromic oxide gels before as well as after associating them with varving amounts of water and methyl alcohol. The thermal effect in the case of dry adsorbents was more with methyl alcohol than with water, and for a given liquid was found to depend upon the surface area of the adsorbent which, in fact, could be thus estimated. The measurement of heats of wetting of the solid as a function of the amounts of liquids previously adsorbed permitted calculations of heats of adsorption of monolayers of liquid (from the liquid phase) and isosteric heats of adsorption. There is no relationship between the heat of adsorption of a liquid in the monolayer and its heat of fusion, as pointed out by previous workers. isosteric heats of adsorption are positive and tend to drop to zero after the completion of the monolaye