The Heat of Immersion Applied to the Study of the Surface Properties of the Surface-Treated Oxide Powders

Abstract

The surface properties of the surface-treated oxide powders were investigated by means of the heat of immersion in water, benzene and in n-heptane, of the samples which were confirmed to be lyophilic by the fact that they tended to disperse into organic medium of the immiscibly mixed media like benzene and water, and of which the surface-radicals were also confirmed. Increasing the length of carbon chain of surface radicals, the heat of immersion in water shows decrease, whereas the immersion in benzene or in n-heptane shows increase. On the surface-treated samples, the heat of immersion in n-heptane is larger than in water, whilst the heat of immersion in water is larger than that in n-heptane on native oxides. In this way it would be possible to determine whether the sample is hydrophilia or lyophilia by comparing the heat of immersion whether it is in water or in n-heptane, except the sample treated by the ethanol. In the case of the sample treated by ethanol, it may be caused by the entropy term that the sample is lyophilic whilst the heat of immersion in water is larger than that in n-heptane. In connection with this, it is much more advisable to use the free energy of immersion than to use its heats in order to determine the surface properties.