Measurement of High Concentration of Hydroxide Ion by Using Polarization Conductance of Aluminum

Abstract

A new method of evaluating the nature of a solution by using corroding behavior of metal has been proposed and named as corrosometry by one of the present authors (S. A. ). This paper deals with the applicability of corrosometry to the measurement of a concentration of hydroxide ion. The polarization conductance of aluminum electrode in an alkaline solution under natural corroding conditions was measured by applying a square wave current of small amplitude. It was found that the polarization conductance was proportional to a concentration of hydroxide ion in the range from 10^-4 to 10^-1mol. dm^-3. The proportional constant was affected neither by oxidation-reduction conditions of a solution nor by the presence of chloride ion.
The polarization conductance was stable without detectable drift during two hr. Thus, aluminum electrode could be used as a hydroxide ion sensor. The unknown potential, arising in the measuring system, did not give any error to this sensor. The sensitivity of this sensor for a hydroxide ion concentration remained constant, while that of glass electrode decreased with increasing concentration. The low electrical impedance of this sensor made this more advantageous than glass electrode from the point of view of industrial measurement. Considering these features, this sensor would be useful for the measurement of a high concentration of hydroxide ion in the industrial field where glass electrode do not operate adequately.