Search for isotope effects in heavy-ion diffusion in liquids

Reference is made to Miller (Nature 243 : 32 (1973)) who found that UO22+ ions diffusing in aqueous solution showed an isotope effect, and also that heavier ions diffuse faster than lighter ions. Miller attributed this to kinetic effects in the molecular diffusion process. The effects should apply generally to heavy ions diffusing in light solvents, and it was thought that the difference in diffusion coefficients should be measurable. Experimental work is here reported designed to test this supposition. The heavy ions chosen for study were the pairs 125I- -131I- and 134Cs+ - 137Cs+, and diffusion coefficients for these ions were measured using the magnetically stirred diaphragm cell method. Conditions varied were temperature, concentration, and type of diffusion. Results are shown tabulated, and showed no detectable isotope effect under a variety of conditions. (U.K.)