Surface tension and 0.1 MPa density of 1-alkyl-3-methylimidazolium tetrafluoroborates in a homologous series perspective

•Investigation of the density and surface tension of [CnMIM][BF4], n=3,5,7,9,10,12n=3,5,7,9,10,12.•Experimental densities at 0.1 MPa and temperatures from (263 to 365) K are presented.•185 experimental Wilhelmy plate and du Noüy ring surface tension values are presented.•Group contribution models to generate recommended density and surface tension values.•The worst-case error is 0.1% for the density and 0.3 mN·m−1 for the surface tension.

Experimental data over the temperature range from (263 to 365) K are presented on the 0.1 MPa density and air–liquid surface tension for 1-Cn-3-methylimidazolium tetrafluoroborates with n=3,5,7,9,10n=3,5,7,9,10 and 12, 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 UcUc not exceeding 0.6 kg·m−3 (6·10-4ϱ6·10-4ϱ). The surface tension data were obtained by the Wilhelmy plate method with UcUc from 0.04 to 0.12 mN·m−1 for n=3n=3 and n=12n=12, respectively, and by du Noüy ring method with UcUc from 0.17 to 0.8 mN·m−1. The Krűss K100 Mk2 tensiometer was used to determine the buoyancy and surface tension forces. The new data allowed to identify the most credible density and surface tension values for 1-Cn-3-methylimidazolium tetrafluoroborates with n=2,4,6n=2,4,6, and 8. Empirical models rooted in group contribution and parachor concept are reported, generating recommended values for the 0.1 MPa density and the surface tension for members of the studied homologous series. The worst-case error of the recommended values of the density and surface tension are estimated to 0.1% and 0.3 mN·m−1, respectively.