The differential capacitance at the electrode electrolyte interface were measured with dropping mercury electrode（D.M.E.） in 1.0 M sulfuric acid and sodium sulfate solutions with various concentration of pinacol and 30 mM of 2, 3-butanediol, ethylene glycol. In acidic and neutral solutions, the differential capacitance vs. potential curves were treated Frumkin-Damaskin adsorption isotherm. Then we calculate coverage of D.M.E. and maximum surface excess on mercury at a>0, obtained from D.M.E. measurement in solution 1.0 M sulfuric acid and sodium sulfate with various concentration of pinacol and 30 mM of 23-butanediol and ethylene glycol.