Surface tension and 0.1 MPa density for members of homologous series of ionic liquids composed of imidazolium-, pyridinium-, and pyrrolidinium-based cations and of cyano-groups containing anions

Abstract

Experimental data over the temperature range from (263 to 365)K are presented on the 0.1MPa density and air–liquid interfacial tension for four ionic liquids with tricyanomethanide anion and pyridinium-, pyrrolidinium- and imidazolium-based cations, still poorly or even not studied in these respects at all. The reported density data were obtained using a single-sinker buoyancy method with an estimated combined expanded uncertainty at 0.95 confidence level Uc=1.0kgm−3 (7×10−4ϱ). The surface tension data were obtained by the Wilhelmy plate method with Uc=0.08mNm−1 and by du Noüy ring method with Uc=0.3mNm−1. The Krűss K100Mk2 tensiometer was used to determine the buoyancy and surface tension forces. An empirical model is reported generating recommended values for 0.1MPa density of 21 ionic liquids with imidazolium-, pyridinium- and pyrrolidinium-based cation and with four different cyano-functionalized anions. The worst-case error of the generated recommended densities is estimated to 0.1%. The model predicts densities for additional 33 members of the same homologous series, for which there exist no experimental density data. A similar model based on the parachor with estimated worst-case error of 0.6mNm−1 (1%) is reported for the surface tension of the same set of ionic liquids. The scope of the surface tension model and reliability of the generated surface tension values are limited due to too small database of available surface tension data.