A detailed experimental study of equilibrium critical phenomena in krypton was made. Using the method of angle of minimum deviation the refractive index was measured along the coexistence curve, along 16 isotherms above and along 11 isotherms below the critical temperature. The range of the temperature measurements in terms of t the reduced temperature difference from Tc was -6.8 x 10-2 ≦ t ≦ -5.7 x 10-5 and 3.8 x 10-5 ≦ t ≦ 4.8 10-2. The measurements were planned so that the region very near the critical point was covered in most detail. The refractive index was related to the density through the Lorentz-Lorenz relation.
After proper weight assignment, the data were analyzed in terms of the asymptotic power laws. The following values of the critical parameters, exponents and coefficients were determined: Tc = 209.286 ± 0.010°K, Pc = 54.213 ± 0.003 atm., LLc = 0.070588 ± 0.000006, β = 0.3571 ± 0.0008, B = 1.840 ± 0.001 γ = 1.182 ± 0.008, Γ = 0.0835 ± 0.0011; γG’ =1.15 ± 0.01, ΓG’ = 0.021 ± 0.001, γL’ = 1.13 ± 0.01, ΓL’ = 0.025 ± 0.001; δ = 4.25 ± 0.25. The law of the rectilinear diameter was obeyed with its slope = 0.0918 ± 0.0004.
The reduced chemical potential differences and the reduced density differences were calculated. The chemical potential was observed to show antisymmetry for-2 x 10-3 ≦ t < 4.8 x 10-2 and -0.3 < ΔLL < 0.3. The data in this range were analyzed using Widom's equation of state and the closed-form(29) of h(x). The proposed equation was found to fit the experimental data very well.
The predictions of the linear model(32) were also checked and were observed to be consistent with the experimental results.
