In this paper, after a brief introduction to review some general ideas relating to electronic transport in liquids, we review the Hall mobility data that exists in organic liquids. A more extensive review is given in the case of liquefied rare gases where there is sufficient information to compare the experimental results with model calculations. It is shown that when the mobility reaches a maximum as a function of density, the deformation potential becomes zero and new types of phenomena become possible. It is stressed that the same phenomena become important independent of the state of aggregation of matter but depend crucially on the atomic density.