N-METHYLPROPIONAMIDE-WATER SYSTEM . DENSITIES AND DIELECTRIC CONSTANTS AT 20-40 DEGREES

Densities and dielectric constants of the N-methylpropionamide (NMP)-water system were measured at 20, 30 and 40° The curve of excess molar volume of the system vs. mole fraction of water was essentially independent of temperature and had a minimum of -1.32 cm3 at 0.6 mol fraction water. The molar volume of transfer of NMP from the pure liquid to a dilute solution in water had a minimum of -6.0 cm3 at 0.9 mol fraction of water. The dielectric data for the system were analyzed in terms of correlation factors calculated on the basis that the square of the gas-phase moment and the high-frequency dielectric constant for the mixture were linear functions of the mole fractions of the components. The structural properties of the system are discussed with respect to the corresponding data for the mixtures of water with N-methylacetamide, ethanol or acetic acid. NMP and water each exert a strong effect on the structure of the other.