Refractive properties of binary mixtures containing pyridinium-based ionic liquids and alkanols

Refractive indices for six binary systems formed by three pyridinium-based ionic liquids: 1-butylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate or 1-butyl-4-methylpyridinium tetrafluoroborate and two alkanols: methanol or ethanol were measured at four temperatures, T = 293.15, 303.15, 313.15 and 323.15 K. From these data excess refractive indices were calculated and fitted. The excess refractive indices of the mixtures, which were found positive, were related to their corresponding excess volumes. Furthermore, several mixing rules were used to predict both refractive indices and densities of the binary mixtures.