The coagulation of peptised sols by simple electrolytes

Summary  The effect of peptising organic anions and polyelectrolytes on the slow coagulation of (undialysed) insoluble metal salt sols by simple electrolyte is studied quantitatively. The results are satisfactorily explained by theVerwey-Overbeck theory of sol stability. At any peptisor concentration, the coagulation time and stability decrease as a function of the logarithm of coagulant concentration. In the presence of constant coagulant concentration, the stability (relative to that of the unpeptised sol) increases with adsorption of peptisor and varies with the peptisor concentration according to an adsorption isotherm. Thepeptising power of a particular reagent is measured by the relative increase in stability per unit peptisor-sol concentration ratio at low peptisor concentrations.