RELATION BETWEEN STABILITY OF OXIDE AND CLAY DISPERSE SYSTEMS AND THEELECTRIC PROPERTIES OF THEIR PARTICLES

Experimental electro-optic studies of oxides (vanadium pentoxide, aero sil, aluminium and iron oxide) and clays and minerals (bentonite, mont morillonite, kaolinite, palygorskite, sepiolite and mica) disperse sys tems provided data for the dipole moments (induced and permanent) and dimensions of their particles. Both dipole moments and their variation s were mainly related to particle medium interface. The variation of t he particle properties with the addition of surface active substances and polymers in all cases correlated well with the variation of the st ability of the respective disperse systems. This correlation generally included also the electrophoretic mobility which was measured in all cases. However there were exceptions, where the correlation of the sta bility with the extremum in the values of the dipole moments did not c orrelate with the isoelectric point. A typical example of this excepti on was the clay palygorskite to which the cation-active surface active substance cetylpiridiniumchloride was added. This exception was consi dered as evidence for the more essential role of the distribution of t he surface electric charge (the permanent dipole moment) and of the ki netics of its redistribution under the action of an electric field (i. e. the induced dipole moment) for the colloid stability, compared to t he average surface electric charge determined electrophoretically. All other cases where the triple (stability, dipole moments, electric cha rge) correlation was observed should be considered as a consequence of the dominant role of interfacial charge dependent (ionic) component o f the induced dipole moment of the particles. Additionally some consid erations were given for the relation of the relaxation of the particle electric dipole moments to the coagulation kinetics.