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A reduced-state viscosity correlation has been constructed from the available data of the inert gases. For the development of this correlation, the fragmentary experimental data for argon were utilized along the lines proposed for thermal conductivities by Owens and Thodos (21) in order to determine the effect of pressure on viscosity. In addition, the only available low-pressure viscosity data for neon and helium have been incorporated in this correlation to produce for the first time the effect of subatmospheric pressures. This correlation covers the range of pressures included between PR = 40 and P, = 0.015 X 10-~ and extends up to temperatures of T R = 100. It has been found that the effect of subatmospheric pressures on viscosity does not become significant above pressures of 1 mm. of mercury. However, at lower pressures, viscosity is found to decrease rapidly, particularly in the regions below absolute pressures of 0.01 mm. of mercury.Viscosities calculated with the reduced state correlation produce an average over-all deviation of 0.93y0 for neon, argon, krypton, and xenon. In these comparisons the available viscosity data for the gaseous and liquid states of tliese substances have been included. Deviations of the same order of magnitude are produced for helium in the gaseous state; however, these deviations become excessive for viscosities of helium in the liquid state. The application of the final reduced state correlation has been extended to a number of diatomic and polyatomic gases and found to apply well to the diatomic gases only.

Internal cation mobilities of Li + and K + in the system (Li-K)CI were determined experimentally using the counter current eleetromigration method over the temperature range 700-778 K, with initial equivalent fractions of KCI of 0.356, 0.416, and 0.451. The relative difference in internal cation mobilities ofLi + and K + was found to reach as much as 7% in this range.Lithium-aluminum/iron sulfide cells that contain multicomponent molten salt electrolytes such as (Li-K)C1 mixture are currently under development for energy-storage applications (1). During charge or discharge of such cells, composition gradients of ions, Li + and K + are induced within the molten salt by the electrode reactions. As a result, the salt compositions are shifted locally from the liquidus range, and precipitation of a solid phase may occur. In lithium/ sulfide cells, which are operated at a temperature range of 400°-430°C in (Li-K)C1 eutectic, Askew and Holland (2) noted that the lithium electrode was severely polarized when .discharged at high current densities. They conjectured that the polarization was caused by precipitation of LiC1 at the lithium electrode. Willars et al. (3) found that the cell capacity was inversely proportional to discharge rate, and the result was interpreted in terms of electrolyte phase separation at the iron sulfide electrode. Braunstein and Vallet (4) and Pollard and Newman (5) calculated current-induced composition profiles of LiC1 and KC1 in lithium/ sulfide cells containing (Li-K)C1 electrolyte. Furthermore, Vallet et al. (6) predicted a composition profile that indicates an increased KC1 concentration near the cathode. More recently, they presented direct evidence of KC1 precipitation (7). Furthermore, they have shown that the composition profile depends not only on the initial composition of the electrolyte, but also on the current density and distance between electrodes. The high KC1 concentration also favors the formation of J-phase (LiKsFe2~S26C1) in the iron sulfide electrode (8). Transition time required for the separation of the components, which was estimated by Braunstein and Vallet (5), is correlated with the transference number and diffusion coefficient. However, transference number is directly related to the emf because the concentration polarization is involved. Thus it is necessary to know the mobilities of the ions at the operating temperature for accurate determination of the transference numbers. At present, the experimental data reported on the mobilities of Li+ and K + in the system (Li-K)C1 are limited to the temperatures at 913 (9) and 1100 K (10), which are much higher than the normal operating temperature of lithium/iron sulfide cells, i.e., 723 K.In this study, the internal cation mobilities, ~.e., the cation mobilities relative to the common anion, were measured in the system (Li-K)CI at the cell operating temperature range by the counter current electromigration method developed by Klemm (11) and Okada (12).