Densities and viscosities of imidazolium and pyridinium chloroaluminate ionic liquids

► Density decreases but viscosity increases with length of alkyl chain at ionic liquid cation. ► Ionic liquid with position meta of the alkyl chain is considerably more dense and more viscous than para isomer. ► Presence of aromatic function at the side chain of the cation increases both density and viscosity. ► Higher effective molar fraction of AlCl3 increases density and decreases viscosity. ► Mixture of two ionic liquids extend their application over temperatures, in which they are in solid state.