Vacancy Calculation of the Viscosity of Potassium–Ammonia Solutions

The theory of random flights and the Stokes–Einstein expression for translational diffusion are combined to calculate the viscosity of a liquid. The viscosity is inversely proportional to $p_{\upsilon }$ , the probability of a molecular vacancy. $p_{\upsilon }$ is evaluated from a quasilattice model for salt solutions as well as alkali‐metal solutions in liquid ammonia and the contribution to the viscosity $\eta$ which varies linearly with concentration $M$ is calculated. The calculated values of ${\eta }_0^{\text{−1}}{\mathrm{(d\eta \hspace{0.17em}/\hspace{0.17em}dM)}}_0$ of salt solutions are 20%–35% larger than the observed values. Calculated values of ${\mathrm{|\hspace{0.17em}\eta }}_0^{\text{−1}}{\mathrm{(d\eta \hspace{0.17em}/\hspace{0.17em}dM)}}_0\mathrm{\hspace{0.17em}|}$ for alkali‐metal solutions are somewhat larger than the observed values but the coefficients have the correct sign and temperature dependence.