Electrical Conductivity and Viscosity of Aqueous Binary Mixtures of 1-Alkyl-3-methyl Imidazolium Tetrafluoroborate at Four Temperatures

Dynamic viscosity and specific electrical conductivity on three binary systems of 1-alkyl-3-methyl imidazolium tetrafluoroborate [CnMIM][BF4] with water covering all ranges of concentrations are presented. Viscosity was measured at 15.0 °C, 25.0 °C, 35.0 °C, and 45.0 °C, while conductivity was measured at those four temperatures for equimolar mixtures only and at 25 °C over the whole composition range. The alkyl chains of the ILs used were ethyl [EMIM][BF4], butyl [BMIM][BF4], and hexyl [HMIM][BF4]. Note that [HMIM][BF4] is only partially miscible in water at the studied temperatures and atmospheric pressure. Viscosity deviations and molar conductivity were derived from experimental data and fitted to suitable equations. Experimental data were also compared with those previously published, and a good agreement was observed. Transport properties were discussed in terms of Walden’s rule, which is partially correct. This paper complements one recently published by us, where density and surface tension at 25 °C for exactly the same systems are presented. The goal of this work is to study the effect on the transport magnitudes of the alkyl chain length in the n-alkyl methyl imidazolium cation and to compare the two main transport magnitudes.