Heats of immersion of titanium dioxide pigments in alcohol—water mixtures

The heats of immersion of partially dried anatase and rutile pigments in mixtures of water with methanol, ethanol, and n-propanol were measured by a differential calorimetric method. The anatase heats of immersion could best be explained by assuming preferential adsorption of the alcohols, the effect being greatest for n-propanol The rutile pigment, however, appeared to adsorb water preferentially in methanol—water and ethanol—water mixtures over the whole concentration range. In propanol—water mixtures the rutile pigment preferentially adsorbed water below an alcohol mol fraction of 0.25, and preferentially adsorbed propanol at mol fractions of alcohol greater than 0.25. The differences in behaviour between the two pigments may be explained qualitatively from the point of view of their surface morphology.