A description is given of a method developed for diffusion and electrotransport measurements in liquids, which permits several successive readings on a sample in uninterrupted anneal. Errors from solidification and sectioning are avoided, and the reproducibility of measured diffusion coefficients is better than two percent. Experimental results are given for gallium self-diffusion. The present apparatus can be conveniently applied to many liquids solidifying below some 280 °C utilizing gamma tracers with energies in the range 0.2 - 2.0 MeV. The design can be modified for higher temperatures.