Аннотация:Oscillation densitometry is used to determine the densities of a liquid phase at 288.15, 298.15, and308.15 K in binary systems H2O–Ni(CH3SO3)2 and H2O–Co(CH3SO3)2 and corresponding ternary systemscontaining methanesulfonic acid. Density in the H2O–CH3SO3H system is measured only at 288.15 and308.15 K. Parameters of Laliberté model for calculating the apparent volume of liquid phase were determinedfrom the data for the binary systems. Its ability for predicting the volume properties of ternary solutions wasshown.