Instrumental study of electrolytic conductance measurements using four-electrode cells

Summary A new apparatus was presented for the electrolytic conductance measurement by a four-electrode cell under controlled-current or controlled-potential conditions. The four-electrode cell method enables us to dry the whole cell without altering the cell constant and to use electrodes of any material unless they are attacked by the solution. The direct reading of solution resistance can be made with an accuracy of ±0.2%. When the resistance is measured by the null method and calibrated by the method of substitution, the accuracy is increased to better than 0.1% at frequencies less than 1500 Hz, provided that the resistance is less than several kiloohms. It was shown that the d.c. conductance can be determined with a reasonable accuracy by the same measuring apparatus. The present method can be applied to the absolute determination of electrolytic conductivity without calibrating the cell constant by using standard solutions of known conductivities. Because of these advantages, the present method is expected to be very useful in the conductance study of solutions where the conventional two-electrode methods fail to give reliable data.