Electrical Conductivity of Molten Cryolite and Potassium, Sodium, and Lithium Chlorides

Abstract

An improved technique has been developed for the determination of the electrical conductivity of reactive molten salts and has been applied to cryolite. The method employs a platinum cell with two concentric hemispherical electrodes. This cell is maintained a fixed distance below the surface of the molten salt which is held in a larger platinum container. Errors from lead resistance have been eliminated by measuring with a Kelvin double bridge (Thomson bridge) and polarization difficulties have been minimized by extrapolation of the nearly linear plot of resistance vs. frequency−1/2 to infinite frequency. Conductivities of molten potassium chloride, sodium chloride, and lithium cloride were determined with a quartz dip‐cell. Best values for the conductivities (ohm−1cm−1) at 1000°C were: cryolite 2.80; potassium chloride 2.65; sodium chloride 4.17; and lithium chloride at 700°C, 6.14. Densities (g/ml), measured by a platinum sinker, were found to follow these equations from the melting points to 1080°C : potassium chloride 1.964–0.574ċ10−3 t; sodium chloride 1.969–0.524ċ10−3 t; cryolite 3.032–0.937ċ10−3 t. The logarithm of equivalent conductance (A) changed linearly with reciprocal absolute temperature (T). Best values for the activation energy for conductance (kcal/mole) (calculated as 2.303 times 1.986 cal/mole deg times slope of log A vs. 1/T) were: cryolite 4.48; potassium chloride 3.32; sodium chloride 3.04; lithium chloride 1.70. Maintaining the fused cryolite in contact with an atmosphere of argon as compared with room air had a negligible effect upon the measured conductivity values for cryolite.

Electrical Conductance of Single Molten Lithium Halides

“…Figure 2 shows the percent departure of the present data from the recommended data reported by Janz et al in the NBS circular 4 . We note here that the percent difference is calculated as: our value -recommended value As seen in the figure, our data for LiCl are by 2 -3% higher than the recommended data which are based on the combined values of Van Artsdalen and Yaffe 5 and Edwards et alias 6 . However, the temperature dependence is similar in both cases.…”

Conductivities of Room Temperature Molten Salts Containing AlCl3, Measured by a Computerized Direct Current Method

“…These results reveal that these data obey the Arrhenius equation over the temperature range studied. The found activation energies (E.d) are presented in Ta- b le 4 [11,12], which indicates that the binary AICI3-EM IC melts have the lowest conductivity activation en ergy among these mixtures. The results may be ex plained in terms of the degree of planarity and the scale of lattice energy [13,14].…”

“…2 and 3 show that the specific conductivities of the AICI3-BPC and AICI3-EMIC systems increase nearly linearly with the temper ature, which is not the case for the AICI3-BTEAC system ( Figure 4). These conductivities were fitted by the Arrhenius equation [9][10][11][12] …”

High temperature 35Cl nuclear magnetic resonance study of the LiCl–KCl system and the effect of CeCl3 dissolution

“…16 There is no report on the activation energy variation with temperature in the (Li,K)Cl system, but a similar phenomenon was found in the alkali and alkaline earth halide systems such as CdCl 2 -KCl. 15 In these systems, the decrease in the activation energy for motion suggests the dissociation of the ionic complex, and this indicates there are complexes in the molten (Li,K)Cl system.…”

“…These agree, within error, with the activation energies of 0.0746-0.0899 eV (LiCl melt) and 0.1414-0.1489 eV (KCl melt), which were obtained in high temperature equivalent conductivity measurements of LiCl and KCl. 5,12,15 Here the equivalent conductivity is the product of the specic conductivity and the equivalent volume (of 1 mol), and it refers to a state in which there is always one equivalent of the salt between electrodes at 1.0 cm distance. 5,12 Therefore, the activation energy derived from equivalent conductivity is preferred for comparisons of ionic migration.…”