The wetting of angular quartz particles: Capillary pressure and contact angles

A new experimental apparatus for the determination of powder wettability is described. The principle of the technique is based on the measurement of the equilibrium capillary pressure in a packed bed of particles. Using White's thermodynamic approach (J. Colloid Interface Sci., 90 (1982) 536), both the macroscopic solid-solution-vapour contact angle, θ, and the specific surface area, A (m² g^-1), of the powder, can be obtained. Test experiments on angular quartz particles and glass spheres have been performed. A wide range of situations have been covered: hydrophilic and hydrophobic particles wetted with water and a variety of organic liquids. The results show that reliable and reproducible values for θ and A for angular and relatively coarse powders can be obtained with the proposed equipment.