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Revista Brasileira de Ciências Farmacêuticas

Print version ISSN 1516-9332

Abstract

MORA, Carolina P.; LOZANO, Hernán R.  and  MARTINEZ, Fleming. Thermodynamic aspects of partial miscibility between n-octanol and water. Rev. Bras. Cienc. Farm. [online]. 2005, vol.41, n.1, pp.13-26. ISSN 1516-9332.  https://doi.org/10.1590/S1516-93322005000100003.

In the present work the thermodynamic analysis for those data presented by Dallos and Liszi on mole fraction n-octanol-water liquid-liquid equilibria was made. The values were analyzed using the van't Hoff method (ln S as a function of T-1) and those presented by Grant et al. (ln S as a function of T-1 and ln T). A non-lineal behavior was found in all cases studied by the van't Hoff method, which lead us to apply a parabolic regression model derived in order to calculate the enthalpic changes. Endothermic processes were obtained for all temperatures studied. In both systems the free energy changes were positive, whereas the entropic changes were negative indicating some kind of organization in the saturated solutions. In the case of n-octanol-saturated water this result would be explained as the hydrophobic hydration around the aliphatic groups and on the other hand, in the case of water-saturated n-octanol, it could be due to organization of n-octanol molecules around water molecules by hydrogen bonds as it has been presented in literature. The thermodynamic values calculated were compared with those presented by other authors, which were obtained by calorimetry and also by means of equilibrium constants as a function of temperature.

Keywords : n-Octanol-water system; Partial miscibility; Solution thermodynamics.

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