Measurements of the Critical Parameters and the Vapor-Liquid Coexistence Curve in the Critical Region of HCFC-123

Measurements of the vapor-liquid coexistence curve in the critical region were made for HCFC-123 (CHCl₂CF₃) by visual observation of the vapor-liquid interface in an optical cell. Thirty densities of both saturated liquid and vapor were obtained in the range of temperatures from 401 K to the critical temperature corresponding to the density range between 203 and 1141 kg/m³. The experimental uncertainty of the temperature measurements was estimated to be less than ±12 mK, while that of the density measurements was estimated to be between ±0.09% and ±0.53%. Not only the level where the meniscus disappeared but also the intensity of the critical opalescence were considered for the determination of the critical temperature T_cand the critical density ρ_cof HCFC-123 as 456.86 ± 0.02 K and 556 ± 3 kg/m³, respectively. The critical exponent β was also determined, and the correlation of the saturated liquid density of HCFC-123 was established.