A Way of Measuring the Surface Tension of a Suspension of Bentonites

Results are presented from pendant and sessile drop measurements of the dependence of surface tension σ of aqueous suspensions of bentonites on the period of surface formation. It is established that the sedimentation of particles is the most important factor affecting the accuracy and reproducibility of measurements of σ in suspensions of bentonites. A procedure is proposed that neutralizes the effect this factor has on the value of σ. Ways of measuring σ in which sedimentation is directed differently relative to the surface are used. Sedimentation is thus directed to the surface in the pendant drop approach, and away from the surface in the sessile drop technique. Measuring σ in these ways and averaging the results considerably reduces the error caused by sedimentation. Analysis of the concentration dependence of σ on the suspensions of bentonite shows that the sedimentation factor is almost completely eliminated when using this procedure.