Optimum mixture compositions for measurement of cross virial coefficients

Abstract

Random error propagation is examined to determine cross second and third virial coefficients from binary gas density measurements by both the indirect and direct methods. Determination of the cross second virial coefficient B,, from Bm at a single composition via the indirect method is optimized when y:el = y:e2, where e, and e, are the pure component uncertainties. When all errors are equal, the equimolar mixture is optimum as expected.Corresponding analysis of the cross third virial coefficients, C1,2 and C, , , ,show that the optimum compositions are not (V3, V3) as expected for equal error distribution, but rather (%, 3/4). Equations presented allow determination of the two optimum compositions, when em varies with composition. Minimization of the combined errors in B,,, C, , , , and C,22via mixture measurements at two compositions provides results near (V3, V3), when all errors are equal. Methods for direct measurement of B,, are reexamined. Optimal compositions are found using third virial coefficient correlations.

Vapor-Phase (p, ρ, T, x) Behavior and Virial Coefficients for the Binary Mixture (0.05 Hydrogen + 0.95 Carbon Dioxide) over the Temperature Range from (273.15 to 323.15) K with Pressures up to 6 MPa

“…Our data, together with those from Cottrell et al, Boerboom and colleagues, , and Abadio and McElroy agree within their mutual uncertainties and lie within the value range of the GERG-2008 EOS. This is good agreement despite the difficulty in acquiring good accuracy for B 12 ( T ) with a 95/5 composition ratio, as described by Eubank and Hall …”

“…This is good agreement despite the difficulty in acquiring good accuracy for B 12 (T) with a 95/5 composition ratio, as described by Eubank and Hall. 47…”

Global ab Initio Potential Energy Surface for the O2(3Σg –) + N2(1Σg +) Interaction. Applications to the Collisional, Spectroscopic, and Thermodynamic Properties of the Complex

“…However, the contribution of the anisotropy is more important in the ab initio than in the experimentally derived PES, which in turn compensates the isotropic contribution and globally leads to a good agreement with the experimental B(T). Because second virial coefficient measurements for gas mixtures are in general less accurate than those for pure gases 48 we find it useful to provide data for temperatures higher than those considered in the experiments, as shown in Table 4. On the basis of the previous analysis, we believe that present results for the second virial coefficients B(T) are the best theoretical estimates to date for temperatures higher than 353 K and, for T > 500 K, they should be taken as the reference data.…”

“…Because second virial coefficient measurements for gas mixtures are in general less accurate than those for pure gases we find it useful to provide data for temperatures higher than those considered in the experiments, as shown in Table . On the basis of the previous analysis, we believe that present results for the second virial coefficients B ( T ) are the best theoretical estimates to date for temperatures higher than 353 K and, for T > 500 K, they should be taken as the reference data.…”

Global potential energy surface for the O2 + N2 interaction. Applications to the collisional, spectroscopic, and thermodynamic properties of the complex

“…However, the contribution of the anisotropy is more important in the ab initio than in the experimentally derived PES, which in turn compensates the isotropic contribution and globally leads to a good agreement with the experimental B(T ). Since second virial coefficient measurements for gas mixtures are in general less accurate than those for pure gases [48] we find useful to provide data for temperatures higher than those considered in the experiments, as shown in Table IV. Based on the previous analysis, we believe that present results for the second virial coefficients B(T ) are the best theoretical estimates to date for temperatures higher than 353 K and, for T > 500 K, they should be taken as the reference data.…”