A rectangular micro-electrophoresis cell is commonly used for measuring the zeta-potential of mineral particles in suspension. It is thus important to analyse the electro-osmotic circulation of the dispersion liquid in the cell for determining the electrophoretic velocities of suspended solids. A theoretical calculation of this circulation was presented by Smoluchowski (1921), Komagata (1933) and White(1937). By using method of measuring electrophoretic velocities based on the above three theories, serious errors are obvious. Then, Mori and Okamoto (1980) have proposed a unified theory for determining the precise electrophoretic velocity of mineral particles in a rectangular cell, based solely on the coefficients of the velocity distribution curve which is represented by an asymmetrical parabola. By the Mori and Okamoto's method, we determined the relation between the zeta-potential and pH value of suspension for several minerals.

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