Thermophysical properties of the paramagnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate over an extended range of temperature and pressure

The paramagnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate [BMIM][FeCl4] was subject to multiple high-precision thermophysical property measurements under both ambient and high pressure. Density rho(p(0),T) / kg.m(3) and speed of sound u(p(0),T) / m.s(-1) data at ambient pressure were recorded at temperatures T = (278.15 to 343.16) K using a DSA 5000 M combined vibrating tube densimeter and speed of sound analyser with a standard uncertainty of Delta rho(p(0),T) = +/- 0.001 kg.m(3) and Delta u(p(0),T) = +/- 0.1 m.s(-1) , respectively. High-pressure volumetric (p,rho,T) data were measured on an Anton Paar DMA HPM vibrating tube densimeter at T = (273.16 to 413.15) K and at pressures up to p = 140 MPa with an estimated experimental relative combined average percentage deviation (APD) of Delta rho(p,T) / rho(p,T) = +/-(0.01 to 0.08) %. The specific isobaric heat capacity c(p)(p(0),T)J.kg(-1).K-1, a caloric property, was determined at T = (273.15 to 413.15) K with an uncertainty Delta c(p) / c(p) = +/- 0.5 % using a Perkin Elmer Pyris 1 DSC differential scanning calorimeter. To gain knowledge of transport properties, the dynamic viscosity eta(p(0),T) / mPa.s at ambient pressure was recorded at T= (275.03 to 413.18) K by an Anton Paar SVM 3000 Stabinger viscometer and additionally an Anton Paar rheometer MCR 302 device with uncertainties of Delta eta/eta = +/- 0.35 % and Delta eta/eta = +/- 1 %, respectively. The obtained data were first correlated by empirical polynomial equations of state and further processed by the application of classic thermodynamic potentials to determine isothermal compressibility k(T) (p,T) / MPa-1, isobaric thermal expansivity alpha(p) (p,T) / K-1, thermal pressure coefficient gamma(p,T) / MPa .K-1, internal pressure p(int)(p,T) / MPa, specific heat capacity at constant pressure c(p)(p,T) / J.kg(-1).K-1 and at constant volume c(v)(p,T) /J.kg(-1) .K-1, the difference of isobaric and isochoric heat capacity (c(p)-c(v))(p,T) / J.kg (1) .K-1, speed of sound u(p,T) / m.s(-1) and ultimately isentropic exponent k(s) (p,T). This work extends knowledge about the thermophysical properties of [BMIM][FeCl4] particularly to high temperatures and pressures. (C) 2021 Elsevier B.V. All rights reserved.