Experimental Investigation\non the Isobaric Molar Heat\nCapacities of [EMIM][BF<sub>4</sub>] and [HMIM][Tf<sub>2</sub>N] with\nDissolved <i>R</i>32 or R125

An experimental apparatus based on\na flow calorimeter\nwas built\nfor the measurement of the isobaric molar heat capacity (<i>C</i><sub><i>p</i>,m</sub>) of liquids with dissolved gases.\nThe expanded uncertainties of the temperature, pressure, and isobaric\nspecific heat capacity (<i>c</i><sub><i>p</i></sub>) of the experimental system are 0.046 K, 5.0 kPa, and 0.032 J g<sup>–1</sup> K<sup>–1</sup>, respectively. The <i>C</i><sub><i>p</i>,m</sub> of four binary mixtures\nof ionic liquid and refrigerant ([EMIM][BF<sub>4</sub>] + <i>R</i>32, [EMIM][BF<sub>4</sub>] + R125, [HMIM][Tf<sub>2</sub>N] + <i>R</i>32, and [HMIM][Tf<sub>2</sub>N] + R125) were\nmeasured at 290–343 K and refrigerant molar fractions of 0.1–0.6.\nExperimental results show that the <i>C</i><sub><i>p</i>,m</sub> values of such mixtures at the same pressure increase\napproximately linearly with rising temperature and decreasing refrigerant\nratio. The <i>C</i><sub><i>p</i>,m</sub> is much\nmore sensitive to changes in composition than temperature and pressure.\nTwo correlation equations for the <i>C</i><sub><i>p</i>,m</sub> as functions of temperature and component proportions were\ncompared, with average absolute relative deviations of 0.66 and 0.53%,\nrespectively. Furthermore, the excess isobaric molar heat capacities\nof four binary mixtures were analyzed in terms of the pure component\nproperties and molecular interactions in the mixtures.