An Anisotropy Effect in Diffusion under Electric Field

TRACER and self-diffusion investigations under electric field of Li + , Na + , K + , Rb + and Cs + ions in fused alkali nitrates 1 , as also in aqueous-agar gel media 2 , revealed an asymmetry in their spatial distribution following migration: corresponding data for diffusion in the absence of field showed no asymmetry. Present initially as a narrow zone, 2–5 mm. wide, at the origin, the band migrates 30–50 cm. in the field direction, depending on the intensity and the duration of the applied field; the actual displacement of the centre is a measure of the ionic mobility. A plot of the ion concentration as a function of the distance from origin is sensibly Gaussian with a pronounced skew, the arm in the field direction being more precipitous (Fig. 1).