On the determination of the surface free energy of quartz

Studies of water vapor adsorption on quartz by the method analogous to the dynamic gas chromatography step profile method are described. The adsorption was determined by changes in the capacitance of the capacitor (detector) between the coverings of which the quartz powder was placed. Prom the adsorption isotherm the film pressure π of the water film on quartz were determined, obtaining $\text{π}{}_{\max }\text{= 380}\text{erg}\text{cm}{}^2$.An interpretation of the π changes in relation to the film thickness and the kind of wetting process has been proposed. It is concluded that the characteristic film pressure values result from the work of spreading, immersional and adhesional wetting and correspond to thicknesses of about 2, 3 and 4 statistical water monolayers, respectively. The maximum π value, however, probably corresponds to the work of quartz- water adhesion + water cohesion work. On the basis of the thus determined values of π_s, π₁, and π_max, the value of the polar component γ_q^p of the quartz surface free energy was determined, using the value $\text{γ}{}_{\mathrm{q}}{}^{\mathrm{p}}\text{= 76}\text{erg}\text{cm}{}^2$. The calculated average of the γ_q^p value equals 115 $\text{erg}\text{cm}{}^2\text{2}$.