EXPERIMENTAL INVESTIGATIONS OF VAN DER PAUW METHOD APPLIED FOR MEASURING ELECTRICAL CONDUCTIVITY OF LIQUIDS

摘要

The four-point probe method, elaborated by van der Pauw, can be applied also in absolute measurements of electrical conductivity of electrolyte solutions. Conductance cells designed and used according to the method have their cell constant dependent on a single geometrical dimension only - the height. One of such designs, with electrodes located in chambers separated from the measuring space of the cell by narrow gaps, has especially advantageous properties as a calculable cell. This was presented in the previous works of the main author of this paper. The analysis performed there indicates that the consistency between theoretical and experimental results is limited by non-ideal properties of applied instrumentation rather than by the principle of the method. This paper presents later experimental examinations of the cell, carried out in the measuring arrangement improved on the basis of the conclusions presented in the former works. Absolute determinations of electrolytic conductivity of 0,01 and 0,1 kmol/m~(3) NaCl solutions were performed. The results obtained confirm the hypothesis that the cell constant of such a cell can be determined from its height with uncertainty of the order of a few hundredths percent.