The Measurement of the Conductance of Electrolytes. V. A Redetermination of the Conductance of Standard Potassium Chloride Solutions in Absolute Units

Abstract

After Kohlrausch had developed his method of measuring the electrical conductance of solutions by means of an alternating current bridge, he undertook with the aid of Holborn and Diesselhorst1 the determination of the specific conductance of seven standard reference solutions in absolute units in order that the results might be available to himself and to other experimenters for the calibration of conductance cells. For this purpose they used two cells whose cross sectional areas, a, and length, l, were determined mechanically. The cell constant, l/a, could then be computed in absolute units (cm.""1) from the measured dimensions.The cell constants of a considerable number of other cells with sealed-in electrodes of the usual type were determined electrically by comparison with the primary cells by measurements of resistance when filled with a common solution. These cells, whose cell constants were thus determined indirectly, were then used for the determination of the specific conductance of the seven standard reference solutions at approximately 0, 9, 18, 27 and 36°. The specific conductance of each of these solutions for every degree between 0 and 36°was obtained by interpolation. No actual measurements were made at either 20 or at 25°. The water-bath used to fix the temperature of the cells was not provided with an automatic thermostatic control. The majority of the data on conductance in the literature are based on the values ascribed to these standard reference solutions by Kohlrausch, especially the 1 N and 0.1 N potassium chloride solutions.In the original paper by Kohlrausch, Holborn and Diesselhorst it is stated that the normal potassium chloride solution was prepared by dissolving 74.555 g. of potassium chloride weighed in air and making up to 1 liter at 18°. The 0.1, 0.02, and 0.01 normal solutions were prepared by dilution by volume. The book "Das Leitvermógen der Elektrolyte" by Kohlrausch and Holborn,2 which was published in the same year as the paper referred to, contains alternative directions for the preparation of these solutions by weight. This book has probably been used by other experimenters more than the original paper because it is more generally available.Kraus and Parker3a have pointed out that the alternative instructions for preparing the 0.1, 0.02 and 0.01 normal solutions given by Kohlrausch and (X) F.

THE ELECTRICAL CONDUCTIVITIES OF SOME TETRA-n-ALKYLAMMONIUM SALTS IN ACETONITRILE

“…They were intercompared and finally standardized against aqueous solutions of purified potassium chloride. The specific conductivities of the solutions were calculated from the concentrations by means cf the empirical Shedlovksy equation (10) corrected to the Jones and Rradshaw standard (11 …”

Electrochemical analysis section :

“…The essential requirement of an extrapolation formula is that the high frequency limit R, correspond closely to the [49] and inductive [50] cells have been used to avoid polarization effects completely but these require specialized measuring instruments and are not suitable to our ultimate objective of redetermining the Jones and Bradshaw [51] Solutions and Filling of Cells Two solutions were used: demal potassium chloride [51] sealed in 100-cm ampoules and Standard Sea Water, Lot P50, which is supplied in double-necked 250-cm ampoules [52] . Our experience has confirmed the observation that a major source of random error is in the filling of cells [53].…”

Molality-based primary standards of electrolytic conductivity (IUPAC Technical Report)

“…The existing primary standards of electrolytic conductivity are based on measurements of Jones and Bradshaw [1]. These standards consist of solutions of a defined concentration on the so-called demal scale, which is used only for electrolytic conductivity.…”

“…Parker and Parker calculated the corresponding apparent masses of KCl and of H 2 O (at 0°C), uncorrected for air buoyancy, for 0.01, 0.1, and 1.0 demal solutions. Masses (corrected for air buoyancy), calculated based on the atomic weights of 1933, were later recommended by Jones and Bradshaw: 0.745 263, 7.419 13, and 71.1352 g, per kilogram of aqueous solution, for the 0.01, 0.1, and 1.0 demal solutions, respectively [1]. These mass values have been retained through the present day [3,4].…”

“…No uncertainty was assigned to the original absolute values of Jones and Bradshaw [1], which were determined by a chain of at least three separate Jones-type cells with optimized K values. A modern estimate of the uncertainty in the Jones and Bradshaw values is u i = ≥0.02% [6].…”