Water-alcohol miscibilities

A. Chand

The liquid-liquid equilibrium (LLE) data for water with active, racemic and nonracemic alcohol systems were measured by analytical, calorimetric and synthetic techniques. A new method for purification of alcohols and a semiautomated apparatus for the precise determination of LLE data by the synthetic procedure were developed. Liquid-liquid mutual solubilities of water + organic mixtures were also obtained analytically using both isopiestic vapour exchange and direct two-liquid equilibration techniques. The molar heats of mixing of water + alcohol mixtures and molar integral solution enthalpies were measured with a modified 1KB calorimeter. The differences between the present solubility data and those reported previously have been discussed in terms of impurity effects. 2-Butanol contaminated with n-octane dissolved less water but the presence of cosolvent impurities in 2-butanol resulted in the system being bound by a solubility loop. In general alcohol rich phase solubilities are sensitive to impurities while those in the aqueous phase appear to be largely unaffected. The unusual solubility behaviour of water with (±) 2-butanol at low temperatures was confirmed. The region of liquid-liquid immiscibility of the system lies within the temperature range of 268 K and 387 K. The calorimetric heats of mixing data for this system below 278 K suggested that the molar heat capacity of the system at constant E pressure, CEp,m, was negative. Both active 2-butanol and (±) 2-butanol exhibited identical solubility behaviour with water. The unusual solubility behaviour of water + alcohol systems have been discussed in terms of changes in extent of hydrate formations and racemic compound formations. Both racemic alcohols and tertiary alcohols with water exhibited unusual solubility behaviour in their respective alcohol rich phases.

Water-alcohol miscibilities

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