In this study, the solubilities (C-S) of BzR(3)NX, R=Me, Et and Bu; X = Cl, Br and I, in solvents with a dielectric constant (epsilon) range of 1.991similar to46.68 were measured. In this range of the dielectric constant, the solvent could affect the solubility by up to 10(5)-fold. For BzR(3)NCl, In C-S increase linearly with increasing epsilon when epsilon < 8.0. Besides the solubility, the limiting equivalent conductance (Lambda(0)) and the thermodynamic association constant (K-A) of the above salts and the salts Bu4NX, X = Cl, Br, I and HSO4, in H2O, CH3CN, MeOH, C2H5NO2 and EtOH were also determined using the modified DHO conductance equation. Furthermore, for BU4NCl, both the temperature effect on Lambda(0) and K-A and the solvent effect on K-A and the partition coefficient (K-p) were investigated. The results showed that the association was exothermic; lnK(A) increased linearly with increasing 1/epsilon, and InKp decreased linearly with increasing 1/epsilon.