Despite the recent increase in the number of works addressing the effect of water on the thermophysical properties of ionic liquids (ILs), in particular densities and viscosities, the strong effect of the water content in the region of low water content on these properties requires further study for a deeper understanding of the phenomenon. Densities and viscosities of two imidazolium-based ionic liquids, 1and their binaries with water, for mole fractions up to 0.6, at atmospheric pressure and temperatures from (278.15 to 363.15) K were determined. The densities and viscosities of the pure ionic liquids and their binaries with water were described successfully by using several correlations. An extension to the Ye and Shreeve group contribution method shows a good agreement with the density data. An Orrick-Erbar-type approach and the Vogel-Tammann-Fulcher method were also applied to the experimental viscosity data, presenting a good agreement and allowing the estimation of new group contribution parameters, extending the applicability of these methods to new ILs. For mixtures, the one-constant Grunberg and Nissan equation was investigated for the correlation of the experimental viscosity binary mixture data of ILs + H 2 O, providing a good description of the experimental data using a single parameter for each ionic liquid studied.

One of the potential applications of the ionic liquids (ILs) is their use as lubricants or lubricant additives. The choice of the cation and the anion of the ILs, as well as the side chain design, determine their fundamental properties, which permits us to create tailor-made lubricants and lubricant additives among other functional fluids. In this work we have studied 10 ILs for which we report densities and viscosities from 283.15 K (and for some ILs at lower temperatures) up to 373.15 K. The viscosities of the ILs fall in the range of the applications of hydraulic fluid or lubricants. Four of these ILs were composed by the anion tris(pentafluoroethyl)trifluorophosphate [(C 2 F 5 ) 3 PF 3 ] À and one of the following cations:and trihexyl(tetradecyl)phosphonium [P 6,6,6,14 ] + . Furthermore, three of the ILs contain the anion bis(trifloromethylsulfonyl)imide [NTf 2 ] À and one of the following cations [C 4 C 1 C 1 mim] + , [C 4 C 1 Pyrr] + , or [C 1 OC 2 C 1 Pyrr] + . Two other ILs contain the 1-ethyl-3-methylimidazolium cation [C 2 C 1 mim] + and an alkyl sulfate anion (ethylsulfate [C 2 SO 4 ] À or n-hexylsulfate [C 6 SO 4 ] À ). The last one is composed by [C 4 C 1 Pyrr] + and trifluoromethanesulfonate [CF 3 SO 3 ] À . The experimental values were used to determine the glass-transition temperature and fragility of these ILs and to analyze the capability of two group contribution methods recently proposed by Gardas and Coutinho for the density and viscosity prediction of ILs.

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