The data on internal cation mobilities, it, in the molten binary nitrate systems (Ag, M)N03 and (Ti, M)N03 (M = alkali metal ion) previously obtained by us have been re-examined. In binary alkali nitrates it is known to be well expressed by an empirical equation u = {A/(Vm -17)} exp (-E/RT), where V,,, is the molar volume; while A, V6, and E are constants nearly independent of the cations with which they are mixed. It is found that in melts containing U for the M deviates negatively from this equation, and that with TF, UM deviates positively. Thus, Ag and TV both with relatively high polarizabilities, have opposite effects on UM, that is a tranquilization effect and an agitation effect, respectively. The reason has been interpreted in terms of the high polarizabilities and the difference in the sizes of Ag and TV.