Group additivity for the standard partial molal heat capacities and volumes of polar compounds in methanol at 25°C

Abstract

A flow heat capcity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of benzene and 25 polar compounds in methanol at 25°C. These quantities have been extrapolated to infinite dilution to obtain the standard partial molal heat capacities and volumes. The$\overline C _{p2}^o$ and$\overline V _2^o$ data have been used in conjunction with an additivity scheme previously determined for alkanes. Group contributions were evaluatd for −OH, −NH₂, −COOH, −C₆H₅, C=O, −COO−, −CONH−, −O−, −S−, and −S₂−. The concentration dependences of φ_cp and φ_v of nonelectrolytes in methanol are qualitatively similar but much smaller than in water.