THE EFFECT OF AN ELECTROLYTE ON PHASE-SEPARATION IN COLLOIDS

We consider an influence of the solvent ionic strength on thermodynami c properties and conditions at the onset of instability of a monodispe rse colloid, as well as on the coefficient of mutual Brownian diffusio n of colloidal particles. Special attention is given to collective eff ects due to competition of the particles for ions to be adsorbed, whic h are proved to lead to a noticeable drop in the particle electric cha rge and potential as well as in the ionic strength outside the double electric layers. An increase in the ionic strength above a region of r elatively small electrolyte concentrations favours the phase separatio n of the colloid under otherwise identical conditions and causes the m utual diffusivity to markedly decrease, the more so the larger is the concentration of the particles.