Surface tensions and refractive indices of (tetrahydrofuran plus n-alkanes) at T=298.15 K

The refractive indices n and surface tensions a of liquid binary mixtures { xc-(CH2)(4)O + (1 - x)CH3(CH2)(m)CH3, m = (4 to 8)} were measured at T = 29 8.15 K over the whole concentration range. The densities rho of {xc-(CH2)(4 )O + (1 - x)CH3 (CH2)(8)CH3} were also measured at this temperature. The da ta are discussed in terms of molecular interactions and the chain length of the n-alkane. The Lorentz-Lorenz, Dale-Gladstone, Eykman, Oster, Arago-Bio t, and Newton equations were used to predict the excess molar volumes from the refractometric measurements, as well as a modified Eykman equation with a parameter obtained for each binary system from data for dn/dT, d rho/dT, and rho for the pure components. The most accurate predictions were those of the Oster and parametrized Eykman equations. Surface tensions predicted from measured densities using the Sugden equation and the assumption of mol e-wise additivity for parachor were more accurate (between 2 per cent and 7 per cent) than predictions based on refractive index obtained by combining the Sugden equation and the definition of molar refraction R and adopting the additional assumption of mole-wise additivity for R. (C) 1999 Academic Press.