Density measurements of water – N-methylacetamide mixture at temperatures from 274.15 to 333.15 K and ambient pressure. A comparison of the volumetric characteristics of some amides

Abstract

The densities ρ of the binary mixture of N-methylacetamide with water have been measured in the entire composition range of the mixture liquid state at T = (278.15, 288.15, 298.15, 308.15, 323.15 and 333.15) K at atmospheric pressure (0.1 MPa). The densities were also measured for dilute aqueous solutions of N-methylacetamide (from 0.00455 to 0.05743 mol fractions) at a temperature from 274.15 to 283.15 K, with an increment of 1 K at atmospheric pressure, in order to study the effect of N-methylacetamide on the temperature of the maximum water density. These data were later used to calculate the excess molar volumes .VmE., partial molar volumes of water V1 and N-methylacetamide V2, and to obtain the limiting partial molar volumes Vi∞ and limiting partial molar isobaric expansion of N-methylacetamide EP,2∞. The following volumetric characteristics were then obtained from these values: the shift temperature of the maximum density, Hepler’s constant, the pressure derivative of the second virial coefficient, relative volumetric parameter of hydration. The obtained parameters show the effect of N-methylacetamide on water. The study also included a comparison of these volumetric characteristics for several aqueous solutions of amides: acetamide, urea and N-methylurea. The paper also presents a comparison of these parameters at the changes in the structure of amide molecules.