The specific volume and the viscosity of binary mixtures of methanol+, ethanol+, 1-propanol+, and 2-methyl-2-propanol+ water were investigated as functions of temperature, pressure, and composition.
The specific volume was measured by means of a “high pressure burette” apparatus at temperatures ranging from 283.15 to 348.15K and pressures from 0.1 to 200MPa with an uncertainty of 0.09%. The viscosity was obtained by a falling-cylinder viscometer with an uncertainty less than 2% covering the same temperature range and pressures up to 120MPa.
The specific volume data were correlated satisfactorily by the Tait equation, and thermodynamic quantities such as compression, isothermal compressibility, excess quantities, and partial molar volume were calculated. In these systems, the isobars of the thermodynamic quantities versus composition showed a definite minimum or a maximum, caused by the complex interactions between alcohol molecules and water.
The viscosity of alcohols and mixtures increased with pressure, whereas that of water was almost independent of pressure. The viscosity versus composition isobars showed a maximum at 0.2-0.4mole fraction of alcohols. The viscosity maximum was distinct at low temperatures and pressures, but it disappeared gradually with rising temperature and pressure. The viscosity data were correlated with composition and pressure or density at each temperature using polynomial equations.