Excess thermodynamic functions of binary mixtures of normal and isomeric alkanes (C5 and C6)

Abstract

Measurements of densities and total vapour pressures were made at 298.15 K for five systems: I, n-hexane + n-pentane; II, n-hexane + 2-methylpentane; III, n-hexane + 3-methylpentane; IV, n-hexane + 2,2-dimethylbutane; and V, n-hexane + 2,3-dimethylbutane. Molar excess volumes, v^E, are negative and small for all five systems. The magnitude of v^E diminishes with an increase in the amount of methyl branching. Molar excess Gibbs energies for second and third systems show a very small positive deviation from Raoult's law, whereas the remaining three systems deviate slightly in the negative direction. Analysis was made in terms of theories of solutions.