Osmotic pressure of polysilicic acid dispersion and particle interaction forces

The dependence of the osmotic pressure of a periodic colloidal structure arising in a polysilicic acid solution on a solid phase concentration was studied. Interparticle distances were measured by the small-angle X-ray and neutron scattering methods. From osmotic pressure data the forces of pair interaction between microscopic objects were determined. It was shown that particle repulsion is of ion-electrostatic origin if the interparticle distance is relatively large. In the case of thin liquid interlayers separating interacting surfaces, structural forces should be taken into account. These forces are mainly responsible for the osmotic pressure of concentrated disperse systems. The parameters characterizing the value and range of structural forces were calculated.