Measurement of forces between colloidal particles

Abstract

Apparatus has been constructed for the measurement of the pressure created by disperse systems as a function of the volume concentration of the disperse phase. Experiments with sodium montmorillonite as the colloidal system have enabled the force to be obtained as a function of the distance between the plates down to distances of the order of 10 Å. The results have been compared with those expected theoretically on the basis of the DLVO theory. The forces obtained at distances of less than 50 Å are much greater than those predicted by the theory and the additional force appears to arise from solvation effects in the thin liquid film between the particles. This has been confirmed by carrying out measurements in the presence of a non-ionic surface-active agent, a known stabilizing agent, where the repulsive forces due to solvation are enhanced.