Heats of Solution of Alkali Metals in Ammonia

The heats of solution of sodium and potassium in liquid ammonia are examined in terms of the redox model which has been proposed for the composition of these solutions. The heats of solution are shown to vary in an essentially linear manner with the spin paramagnetic susceptibility of the solutions, as expected from the model. Analysis of the data yields enthalpy changes for the redox equilibrium M++2S−⇌M−+2S, which are in reasonably good agreement with those obtained from the temperature variation of spin paramagnetic susceptibility. A temperature‐dependent enthalpy is indicated for the redox equilibrium.