The influence of different combinations of electrolytes on negatively charged silver iodide sols was studied. Wo. Ostwald1, Tefak 2 , Overbeek 3 , Matijevic 4 , Levine 5 and ot her authors have offered different explanations for these electrolyte effects. EXPERIMENTAL The rate coefficients of coagulation were measured by a light scattering proce-dur e. According to Oster 6 and von Smoluchowski, coagulation is a second order r ate process. The rate coefficient of coagulation is proportional to a

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... change in the intensity of scattered light with relationship to time. It will be assumed that the change in t he relative intensity ratio at 10 minutes of 0.12 corresponds to the same value of t he rate coefficient. The experimental procedure in statu nascendi described by Tefak et al.7 was used. RESULTS In Tables I and II the concentrations of ions which produced the constant value of t he r ate coefficient of AgI/I-sol coagulation are presented. It is assumed tha t ion-pairings and adsorption 9 of the ions on the sol surface could be neglected in the calculations of the bulk solution compositions. The concentration of r-ions in bulk solution was calculated as a difference between the initial concentrations of KI and AgN0 3 solutions. Because the solubility products of AgI is 10-10 mol2 dm-6 almost all the silver was assumed to be in a fo rm of AgI sol. The concentration of Mg 2 + ions is equal to the total concentration of Mg(NOah solution. Ionic strengths were calculated by using the concentrations of the ions presented in Tables. The activity coefficients of Mg2+ ions were calculated by the TABLE I