Phase V–T diagrams of solid freons. Part II: halomethanes

Abstract

Phase V– T diagrams of solid halomethanes R12 (CF2Cl2), R20 (CHCl3), R22 (CHF2Cl), R23 (CHF3), and R30 (CH2Cl2) were constructed using both literature and our experimental data obtained during the study of isochoric thermal conductivity. The carbon tetrachloride V– T phase diagram was presented earlier. The jumps in molar volume during melting and the boundaries of the existence of phases have been determined. At pressures up to several kbar halomethanes R12, R20, R23, and R30 exist in only one crystal modification, whereas R22 shows a shift type phase transition near 59 K, and the high-temperature phase of CCl4 is dynamically orientationaly disordered. Experimental values of thermal pressures ( dP/ dT) V and dPm/ dT on melting line were measured, and they are compared with those calculated by the Clapeyron-Clausius formula.