Pressure at the maximum in adsorption isotherms at high pressures

conclusion ascribed to us by Subramanian,2 namely, that the hydrate, if a clathrate, has a low guest to host ratio.On the contrary, the stability of this hydrate under pressure, the electrically conductive properties of solution permeated solids* and of aqueous tetraalkylammonium halide solutions4 under pressure, and the partial molar volumes of the tetraalkylammonium cations in aqueous solution6 all point to the conclusion that hydrophobic hydration such as that enveloping the n-tetrabutylammonium cation represents a low specific volume type of water structure.This in turn implies that, in order to achieve high density, if the structure is of a clathrate type, then the cages in the host structure surrounding the cations must be filled with one or more water molecules.Also the structure cannot be that of the ordinary hexagonal ice-I, a high specific volume form.If the structure is not ice-like, there is no reason to expect it to facilitate ice formation in the bulk solution.Furthermore the nucleation of supercooled water is a rate, not an equilibrium phenomenon, and examination of Bridgman's phase diagram for water6 shows that there are no stable forms in the temperature and pressure range of the experiments in question.Thus we feel that some explanation other than the nucleation of ice-I must be proposed in explanation of Evans' results,',* but we most heartily agree that, in view of the biological significance of the structure involved, further studies, such as X-ray examination, of these structures should prove to be worthwhile.