Interdiffusion of anions in fused alkali nitrates has been studied with a plane source diffusion technique; the concentration gradients in the diffusion cell being measured with a wave-front-shearing interferometer. By choosing the same cations in the experiments the diffusional mixing of different anions at low concentrations into three alkali nitrates has been studied. The diffusion coefficients of F- and Br- in LiNO3; F-, Br-, I-, CO32-, and SO42- in NaNO3; and I- and CO32- in RbNO3 were obtained over a temperature range of some 100 °C above the melting point of the different solvents.

Interdiffusion coefficients in molten alkali nitrate systems have been measured by recording the phase variations introduced on an initially plane wave front when passing through a diffusion vessel. The recording of the path differences is performed with a wave-front-shearing interferometer giving a high degree of accuracy. Two different methods have been used to initiate bottom layer diffusion experiments, one of which has been developed in the course of this work. The interdiffusion studied here has been that of rubidium and cesium ions and in some cases that of sodium and potassium ions diffusing into the pure melts of lithium nitrate, sodium nitrate, and potassium nitrate. The diffusion coefficients have been measured over a temperature range of some 100°C above the melting point.The marked decrease in fluorescent quantum yield of anthracene in going from crystal to solution is discussed theoretically. The relative importance of direct and indirect radiationless transitions from the excited singlet to the triplet manifold is calculated using a simple model.

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