Surface Chemical Studies of Dispersion and Coagulation of Colloid Particles

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The stability of colloid particles has been one of the most important subjects in colloid and surface science. The interest in stability properties colloidal system has been increasing rapidly due to their utility in modern high-technology including medical application.This cooperative study consists of 18 members who are conducting their own research in a variety of field but are connected with a common subject, i.e., colloid stability. The study consists of two projects; 1) cooperative measurements of critical coagulation concentration, CCC, of polystyrene latex particles which were distributed to each member from one original lot and 2) individual research of their own subjects. Results of the coolerative research are summarized as follows.Mean values of CCC's of negatively charged latex perticles were found to be 230 mM (standard deviation, =52 mM) for K^1, 18.9 mM( = 5.6 mM) for Mg^<2+>, and 0.47 mM( =0.048 mM) for La^<3+>, respectively, in which nitrate salts were used. The ratio … More of these CCC's is 100:8.2:0.20, in fairly good agreement with the ratio predicated by the DLVO theory, i.e., 100:1.6:0.15, except for divalent Mg^<2+> which shows a little larger value. The Hamaker constant of latex particles in aqueous media was evaluated using the CCC and zeta potentials at CCC by applying the DLVO theory. The mean value of the Hamaker constant of latex perticles in aqueous media was obtained as 1.52x10^<-20> J. This value lies between literature values of the Hamaker constants (0.1-11x10^<-20> J) obtained by the colloid stability experiments, but it is four times larger in magnitude than that on the basis of the Lifshitz theory, 0.35x10^<-20> J.The second experiment on CCC determination was carried using different latex particles. The mean values of seven determinations of CCC were found to be 205 mM( =11 mM) for K<@D1+@>D1, 18.8 mM( =0.80 mM) for Mg<@D12+@>D, and 0.51 mM( =0.034 mM) for La<@D13+@>D1, the ratio of CCC being 100:9.1:0.25, respectively. The mean value of the Hamaker constant was obtained as 1.07x10<@D1-20@>D1.J. The second results with much less scattering justfy the first ones. Results of the individual research are referred to the list of publication attached. Less