Tracer studies in the solid state - Diffusion in hydrogen bonded solids

Ubbelohde has proposed a proton transfer mechanism to explain electrical conductivity studies on a series of crystalline organic acids and it has been suggested that conductivity increases with the decree of co-operative hydrogen bonding in the crystal. Experiments have been carried cat to test this hypothesis by studying the conductivity pad the rate of proton diffusion, using tritium as tracer, in the same single crystals of two organic acids exhibiting different degrees of cooperative hydrogen bonding; benzoic acid which exists as a linear chains of in the solid state and acetic acid which has linear chains of cooperative hydrogen bonds extending through the crystal. The acids were purified by distillation, sublimation and zone refining techniques and single crystals were grown from the melt in a Bridgman own Diffusion was studied by a sectioning technique using tritium labelled benzoic and acetic acids to obtain the hydrogen diffusion rates and carbon-14 labelled benzoic acid used to measure the diffusion coefficient of the bulk molecule. The electrical conductivity of benzoic acid was found to be very low in single crystals being less than 10