Experimental study of the isochoric heat capacity of isobutanol in the critical and supercritical regions

Experimental study of the isochoric heat capacity and coexistence-curve singular diameter of sec-butanol near the critical point and Yang-Yang anomaly strength

“…The experimental details (the physical basis and theory of the method, the apparatus, experimental procedures and an uncertainty assessment) of the isochoric heat-capacity measurements have been described in our earlier publications [13][14][15][16][17][18][19][20]. Only a brief review will be given in this study.…”

“…As was shown in these works, this method can also be used to accurate simultaneously measurements of vapour-pressure, P S , PVT, C V VT and thermal-pressure coefficient, V , if the calorimeter additionally supplied with a calibrated extensometer (piezo-calorimeter). Details of the method of quasi-static thermograms and its application to complex thermodynamic systems with different types of phase transitions (pure fluids and binary solutions with L-V, L-L, L-S, V-S, L-S-V and L-L-S phase-transitions) are described in our previous publications [13][14][15][16][17][18][19][20][24][25][26][27]. Synchronous recording of the resistance thermometer (T-plot) and of the sensor of adiabatic control readings follows the thermodynamic state of the sample as it approaches the phase-transition point.…”

“…According to Equation (4), two-phase isochoric heat capacity C V2 is a linear function of specific volume V along the each fixed isotherm (see Figure 7 and also [13][14][15][16][17][18][19][20]), the slopes of which are equal to T d 2 P S =dT 2 À Á , whereas the intercepts for V ¼ 0 are related to ÀT d 2 =dT 2 À Á . Rapid increases of the slopes of C V2 -V isotherms (Figure 7) as the critical temperature is approached, reflect an increase of the second temperature derivative, d 2 P S =dT 2 À Á .…”

“…Therefore, Yang-Yang anomaly strength R directly related with the singular diameter criticality as discussed in the Section 3.3 and can be also found from the asymmetry coefficients in the coexistence curve or diameter singularity (Section 3.3). For propane [7,8], the scaled strength of the Yang-Yang anomaly is R ¼ 0.56, for ethanol [56] R ¼ 0.12, for diethyl ether [25] R ¼ 0.35, for isobutanol [14] R ¼ À0.08, and for tert-butanol [13] R ¼ À0.03. Orkoulas et al [8] estimated the value of the Yang-Yang anomaly strength R for carbon dioxide (-0.35) and propane (0.56) using derived d 2 P S =dT 2 À Á and d 2 =dT 2 À Á from our previously published two-phase isochoric heat capacity data [57][58][59].…”

A molecular dynamics study on the role of attractive and repulsive forces in isobaric heat capacity and sound velocity of sub- and supercritical dense fluids

“…This property is related to thermodynamic properties such as molecular weight [4], molecular radius [5], surface tension [6], structure and dynamics of interface [7], molecular magnetic rotation [8], pseudo-Gruneisen parameters [9] and intermolecular free length [10]. The isochoric heat capacities and sound velocities have been extensively tabled for different fluids [11][12][13][14][15][16][17][18].…”