THERMODYNAMIC ANOMALIES OF CO2 XE AND HE4 IN CRITICAL REGION

A closed-form equation for the chemical potential as function of density and temperature, based on the scaling idea, is fitted to experimental data in the critical regions of Co2, Xe, and He4, optimizing δ, Tc, and two adjustable constants. Values obtained for the critical exponents and the two constants vary only slightly from substance to substance; we find β=0.35-0.36, δ=4.4-4.6, implying γ∼1.25, α∼0.05; ΓΓ′=3.6-4.4, Δ=2.6-3.3. Agreement with previous estimates and with independent Cv and optical-density-gradient measurements is discussed. © 1969 The American Physical Society.