Mutual diffusion coefficients of ethanol + n-heptane and diethyl carbonate + n-heptane from 288.15 K to 318.15 K

The mutual diffusion coefficients of ethanol + n-heptane and diethyl carbonate (DEC) + n-heptane binary solutions were measured over the mass fraction from 0.05 to 0.95 at the pressure of 0.101 MPa, and at temperatures T = 288.15 K, 298.15 K, 308.15 K and 318.15 K. The expanded relative uncertainty (k = 2) of the Mach-Zehnder digital holographic interferometry employed in the measurements was estimated to be less than 2.4% with the confidence level of 0.95. A semi-empirical correlation was used to fit the mutual diffusion coefficients as a function of concentration and temperature, which represents the experimental values with the absolute average relative deviations being 0.94% for ethanol + n-heptane and 0.90% for DEC + n-heptane. The temperature and concentration dependences of the mutual diffusion coefficients were investigated. The strongest non-ideal thermodynamic behaviors appear when the mass fraction of ethanol is within the limits of 0.45 to 0.65 or that of DEC is within the limits of 0.45 to 0.65. Besides, the mutual diffusion coefficients of ethanol + n-heptane and DEC + n-heptane binary solutions are found to be extremely sensitive to the solute concentration over the mass fraction of ethanol and DEC from 0.00 to 0.05, respectively.