Measurements of the Vapor-Liquid Coexistence Curve and Determination of the Critical Parameters for R 114

The measurements of the vapor-liquid coexistence curve in the critical region for R 114 (C₂Cl₂F₄) were made by visual observation of the disappearance of the meniscus at the vapor-liquid interface within an optical cell. Twenty-three saturated densities between 410 K and critical temperature were obtained in the range of densities 290 to 894 kg/m³. The experimental errors of temperature and density were estimated within ±15mK and ±0.5%, respectively. On the basis of these results, the critical temperature T_c and the critical density ρ_c for R 114 were determined to be 418.78 K and 576 kg/m³, respectively, in consideration of the disappearing meniscus level as well as the intensity of the critical opalescence. The critical pressure P_c for R 114 was calculated to be 3.252 MPa by the available vapor-pressure correlation with the present value of T_c. In addition, the critical exponent β and the law of rectilinear diameter near the critical point were also discussed.