Refractive Indices of the Binary Systems

Experimental values of excess molar volume and change of refractive index of binary mixtures were correlated by Redlich-Kister equation (Ottani and Comelli, 2005). The binary contribution was used to correlate the experimental ternary results with the Cibulka equation (Al-Jimaz et al., 2004). Several methods to predict density and refractive index of mixtures were applied to test their validity in the systems studied. 

Density measurements for ethanol were carried out at several temperatures to obtain parameters in some predictive density methods. 

The chemicals ethanol, toluene 99.5% were supplied by Aldrich. The purity of all chemicals was checked by gas chromatography (GC) and the results of these analysis showed that the impurities did not exceed 0.2 mass%. The pure components were degassed ultrasonically. These reagents were used without further purification. Further verification was realized by ascertaining the constancy of the values of density and refractive index for every component at 298.15 K, which were reasonably in accordance with values found in the literature. (Grunberg and Nissan, 1949 Heric and Brewer, 1967 McAllister, 1960 Redlich and Kister, 1948 Tasiae et al., 1992). 

The samples were prepared using a Mettler AE 200 balance with an accuracy of 0.0001 g, covering the whole composition range of the binary and ternary mixtures. Precautions were taken such as using samples recently prepared and reducing the vapor space in the vessels to a minimum, in order to avoid preferential evaporation during manipulation and subsequent composition errors. Tte accuracy in the determination of the mole fraction of the measured samples was also 0.0001. 

The densities of pure components and their nrixtures were measured with an Anton Paar DMA 55 densimeter, and the refractive indices with an Abbe refractometer Type 3T., with accuracies of 0.01 kg my3, and 0.0002, respectively. Each apparatus was matched to a Julabo circrrlator with proportional temperature control aird an autonratic drift correction system that kept the samples at desired temperature usually 298.15 K with accuracy of 0.01 K. The densimeter was calibrated periodically with distilled water and dry air. 

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Bouzas, A., Burguet, M.C., Montdn, J.B., and Munoz, R. Densities, viscosities, and refractive indices of the binary systems methyl fert-butyl ether -t 2-methylpentane, + 3-methylpentane, + 2,3-dimethylpentane, and + 2,2,4-trimethylpentane at 298.15 K, / Chem. Eng. Data, 45(2) 331-333, 2000. 

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