Diffusion studies in liquid potassium and rubidium

Abstract

Self-diffusion coefficients were determined for liquid potassium and rubidium. The types of measurements made were self-diffusion of K and Rb as a function of temperature at one atmosphere pressure, the pressure dependence of self-diffusion coefficients of K and Rb, and the temperature dependence of selfdiffusivity at constant molar volume. The self-diffusion coefficients in liquid K and Rb at 1 atmosphere pressure could be represented by the following expressions. D K (354° K−868° K) = −2·443 × 10 5 + 5·344 × 10 −10( T° K) 2 cm 2/ sec D Rb (337° K−856° K) = −1·479 × 10 −5 + 3·824 × 10 −10( T° K) 2 cm 2/ sec. The empirical equation for both K and Rb may be expressed as D D m = 1.665 [( T T m ) 2 − 0.399] . The linear dependence of D vs T 2 for both Rb and K, observed in the present investigation, tends to offer support to the predictions of the fluctuation theory proposed by Swalin. The experimental data also agree quite well with the dense gas-like model of Ascarelli and Paskin. The activation volumes calculated from the data were 1.5 ± 0.5 cm 3/ mol and 1.2 ± 0.4 cm 3/ mol for liquid K and Rb respectively.