No abstract

The electrokinetic behavior of several positive and negative inorganic colloidal systems has been studied in the presence of anionic and cationic surface active agents. Both electrophoretic and streaming potential methods were employed in the investigation. The inorganic systems and the surface active agents were prepared and purified by methods cited in the literature, and were the subjects of a stability study that has been reported previously. Iron(II1) oxide and aluminum oxide were used as positive colloidal systems and manganese dioxide and arsenic( 111) sulfide as representatives of negative systems. Potassium salts of a series of fatty acids, sodium alkyl sulfates, alkyl amine hydrochlorides and alkylpyridinium chlorides were emplo ed a8 colloidal electrolytes. A slit-ultramicrosco e was used for the electrophoretic measurements and a modification o r t h e apparatus described by Briggs was used for &e streaming potential determinations. The concentration of surface active agent required to decrease the mobility of the particles to zero called the isoelectric concentrations (IEC), was determined by plotting mobility of particles against concentration of surfactant. Plots of the logarithms of the isoelectric concentrations against chain length yielded straight lines in most cases. The curves could be represented by an equation of the type log (IEC) = A + B N , where A is a constant for each homologous series, B is a general constant, and N is the number of carbon atoms in the hydrocarbon chain. Streaming potential studies were limited to iron(II1) oxide and aluminum oxide owders with potassium laurate and sodium dodecyl sulfate as electrolytes. There wa8 poor agreement between the resuis from the two different types of measurements, which was attributed to the different methods of preparing the inorganic substances in the two cases. IntroductionStudies of the effect of pure surface active compounds on the stability of dialyzed inorganic colloidal suspensions, and of the effect of the inorganic substances on the critical concentration of surface active agents2 indicated that the properties were electrical in origin and suggested the present investigation.The literature contains references to the coagulation and recharging of the inorganic substances, iron(II1) oxide3+ and arsenic(II1) sulfide3t4 with univalent surface active ions of sign opposite to that of the original particles, but no systematic study of the effect of the higher chain length compounds on the electrokinetic behavior of colloidal inorganic substances appears to have been made.