ADDITIONAL SURFACE CONDUCTANCE OF THE WEAKLY CHARGED POROUS SURFACE-LAYER OF A COLLOIDAL PARTICLE

Additional surface conductance is the excess of total surface conducta nce over the conductance of a diffuse electrical double layer. Theoret ical estimation of this value is based on the notion of the porous lay er of a colloidal particle. The charge of the porous layer is describe d by the Stern-Langmuir isotherm. Specific calculations have been made for the particular case of the low Donnan potential of the gel layer. It was established that interfacial potential difference is mostly lo calized in a medium (gel or solution) where screening is less effectiv e. This fact is responsible for the possible appearance of a maximum a t the concentration dependence of a zeta-potential. In this case, addi tional surface conductance exceeds Bikerman's conductance: the pattern of the concentration dependence in the first case is governed by the coverage of adsorption sites for potential-determining ions.