Electrokinetic studies of magnesium hydroxide.

The electrophoretic mobility of magnesium hydroxide was studied as a function of the concentration of its potential-determining ions, namely, of the magnesium ions, and of the hydroxide ions or pH. The zero point of charge was located at approximately 10.8. The zeta-potential of magnesium hydroxide below this pH was positive. The addition of magnesium nitrate to magnesium hydroxide suspensions increased the positive zeta-potential and lowered the pH. The low solubility of magnesium hydroxide in water prevented the attainment of substantial concentrations of magnesium ions in solution. Increasing the hydroxide-ion concentration or the pH produced charge inversion. The largest negative zeta-potential was attained at pH 11.5. Further increases in pH produced no significant increase in the negative value of the zeta-potential.