STUDIES OF SURFACE FREE-ENERGY OF CELESTITE

The surface free energy of celestite was determined by the method of ' 'thin-layer wicking'' based on Washburn's equation. The values of inte ractions were determined according to the technique recently proposed by van Oss et al.. Measurements of the penetration time were made for decane, water and formamide. Linear dependences of the penetration tim e were obtained as a function of the square of the distance at which t he liquid penetrated. The penetration rates of liquids for bare surfac e are higher than for that precontacted with vapours of these liquids. The apolar component, gamma(s)(LW), of Lifshitz-van der Waals is 46.3 8 mJ/m(2), and the electron-donor component, gamma(s)(-), equals 66.4 mJ/m(2), while gamma(s)(+) is zero. The determined components show tha t celestite surface is monopolar of distinct electron-donor parameter resulting from hydrogen bonding interactions.