SURFACE AND INTERFACIAL-TENSIONS OF AQUEOUS DISPERSIONS OF CHARGED COLLOIDAL (CLAY) PARTICLES

We have measured (du Nouy ring and maximum bubble pressure methods) su spension-air surface tensions of aqueous suspensions of montmorillonit e and have observed that these surface tensions are larger than those of pure water at the same temperatures. Further measurements have show n that dispersed montmorillonite also increases the suspension-toluene interfacial tension compared with that of pure water-toluene. Similar measurements on aqueous suspensions of kaolinite have yielded sus pen sion-air interfacial tensions with uncertainties as large as the obser ved (small) effect, and also shown that the suspension-toluene interfa cial tension is decreased (opposite to the effect of montmorillonite) by amounts larger than the experimental uncertainties. Measurements of maximum bubble pressures at different flow rates have provided inform ation about the effect of surface age on observed surface tensions.