Viscosity of two binary electrolyte mixtures with common cations and two without common ions (each in three different proportions) as well as the viscosity values for solutions of three simple electro­lytes are reported. Conger and Fume' limiting law for mixed ionic solutions has been established in these cases and en equation of the Jones and Dole type applied to the results. The coefficient of the square root term 'A' has been shown to be a linear function of composition. The same is true of the coefficient of the linear term 'B'. except in the case of NaCI-BaCI2 mixtures. whose results are taken from a previous paper. The additive principle is not applicable to the viscosity of a mixed solution of two electrolytes. the observed values being systematically too low.