No abstract

No abstract

No abstract

Experimental liquid-liquid miscibility temperatures as a function of mole fraction are reported for binary systems formed by methanol as common component with hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and cyclohexane. All the studied coexistence curves present an upper critical solution temperature (UCST). The UCST of the binary systems presents a clear dependence with the molecular shape of the hydrocarbons (e.g., the solubility of the alkanes in methanol increases as branching increases in the structural isomers); hence, 2,2-dimethylbutane shows the lowest UCST with methanol. Cyclohexane presents the highest UCST with methanol (i.e., it shows the lowest mutual miscibility for the six studied systems). Values of the UCST have been calculated with the Weimer-Prausnitz modification for polar components of Hildebrand's Regular Solutions Theory. The predicted UCSTs compare well with those obtained experimentally.

Density measurements have been made by means of a vibrating tube densitometer, at 298.15 K, over the whole composition range for 25 binary liquid mixtures of propanenitrile, butanenitrile, pentanenitrile and hexanenitrile with several different hydrocarbons. Values of the molar excess volume, V E , were derived and the results show a regular pattern of behaviour for each of the four sets of binary system. For a given alkanenitrile, the magnitude of V E increases with the hydrocarbon chain length and also for a given hydrocarbon, V E decreases with the chain length of the nitrile. The PrigogineFlory-Patterson theory was applied to analyse the experimental behaviour by calculating three different contributions to VE, i.e. interactional, free volume and internal pressure. The theory is capable of reproducing the main features of the experimental VE results by using a fitted binary interaction parameter.