The mol. vol. Vm (i.e., the sum of the ionic vols. Vion of the constituent ions) of an ionic liq. (IL) in combination with an anion-dependent empirical relationship is all one needs to predict phys. properties such as viscosity, cond., and d. of [N(CN)2]-, [BF4]-, [PF6]-, and [N(SO2CF3)2]- ionic liqs., including those which may as yet only exist on paper.