The sorption of water and toluene vapours on gram powder (Cicer arietinum) has been studied with a view to ascertaining the fate of the sorbed vapour. Three samples of powder (alkali-washed, toluene-washed and untreated) have been used. The isosteric heats of sorption have been deter­mined. It appears that at least the first lots of water vapour taken up correspond to persorp­tion rather than capillary or multi-layer condensation. Alkali-washed and toluene-washed samples show similar

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... of sorption over the untreated powder. The heat of sorption decreases sharply from over 20,000 cal./mole at low values of sorption to about the latent heat of condensation of high values.