Abstract
New experimental viscosity data are presented for aqueous solutions of methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol (t-butyl alcohol) in the temperature range from 283 to 348 K and pressures up to 120 MPa. The viscosity measurements were performed using a falling-cylinder viscometer on a relative basis with an uncertainty of less than 2%. The viscosity of pure alcohols and aqueous solutions is found to increase almost linearly with increasing pressure, whereas that of water decreases slightly with pressure at temperatures below 298 K. As for the composition dependence of the viscosity, a distinct maximum appears near 0.3–0.4 mole fraction of alcohol on all isobars at each temperature. The viscosity maximum shifts gradually to a higher alcohol concentration with increasing temperature and pressure. The isobars of aqueous 2-propanol and 2-methyl-2-propanol solutions have another shallow minimum near 0.9 mole fraction of alcohol below 323 K. The experimental results were analized empirically by a Tait-type equation and a free-volume theory. It was found that the isothermal viscosity data were satisfactorily correlated by these equations as functions of pressure and composition or of density and composition.
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