SURFACE FREE-ENERGY OF SOME LEAD COMPOUNDS COMPARED TO GALENA

Measurement of contact angles for water, formamide and diiodomethane w ith lead compounds of sulfate, thiosulfate, oxide and hydroxycarbonate were made on both dried and prewetted galena surfaces. Using the valu es obtained, Lifshitz-van der Waals and Lewis acid-base (electron acce ptor and electron donor) components of the surface free energy of the solids were determined, and compared to the values of the surface free energy of nonoxidized and oxidized galena. It was found that the free energy of the galena surface originated from apolar and polar interac tions, and that polar interactions were strongly dependent on the surf ace hydration. Moreover, it may be concluded that the wettability of g alena depends on the lead compounds formed on its surface as a result of the oxidation process, and on the degree of their hydration.