Densities and viscosities were measured at (293.15, 298.15, and 303.15) K for the temary system NaCl + LaCl3 + H2O and its binary subsystems NaCl + H2O and LaCl3 + H2O. The results were used to test the applicability of simple equations for the densities and viscosities of the multicomponent solutions. The predictions agree well with measured values, implying that the densities and viscosities of the examined electrolyte solutions can be related to those of their constituent binary solutions using the simple equations.