Adaptation of (h, T) Data To Calculate Some Thermodynamic Properties of SF6 on the Saturation Curve

Abstract

Information is presented on the behavior of the SF₆ density on the binodal in the asymptotic vicinity of the critical point 3 × 10^–6 < τ < 2 × 10^–4, where τ = (T_c – T)/T_c is the relative temperature, and T_c is the critical temperature. The densities of the liquid (ρ_l) and vapor (ρ_g) phases were calculated based on the experimental data of Garrabos et al. (2018) on the height h at which the meniscus is located separating the two phases of the sample in a horizontal cell of diameter d at a temperature T under the terrestrial gravity. The second component of the method was the order parameter f_s(τ) in an analytical form, which meets conditions of the scaling theory (ST) of critical phenomena and is based on the (ρ_l, ρ_g, T) data of Funke et al. (1998) on SF₆ in the range of 10^–3 < τ < 0.3. A number of problems were formulated, including the construction of the dependences ρ_l(τ) and ρ_g(τ) those are consistent with ST and correlate with the (h, T) data at 10^–6 < τ < 10^–3. The relationship was studied between the (h, T) data and the functions  f_s(τ) and f_d(τ) (f_d is the average or rectilinear diameter). The temperatures dependences of ρ_l and ρ_g were constructed in the range of 10^–6 < τ < 10^–3 .