Densities and Excess Volumes of the 1,3-Dimethylimidazolium Methylsulfate + Methanol System at Temperatures from (313.15 to 333.15) K and Pressures from (0.1 to 25) MPa

Densities of pure 1,3-dimethylimidazolium methylsulfate ionic liquid [MMIM][CH 3 SO 4 ] and its mixtures with methanol have been measured with an accuracy of ±0.2 kg·m -3 over a temperature range from (313.15 to 333.15) K and a pressure range from (0.1 to 25) MPa using a vibrating tube densimeter. The isothermal compressibilities, isobaric expansivities, and excess volumes have been calculated. The uncertainties of these properties have been estimated to be ±0.05 GPa -1, ±0.2·10 -4 K -1, and ±0.1 cm 3 ·mol -1 . The exceptionally strong influence of pressure and temperature on the excess volumes has been observed.