The second virial coefficients of organic vapours

Abstract

The compressibilities of a num ber of organic vapours have been measured at pressures up to 1 atm. and temperatures ranging from 40 to 130° C. The observed second virial coefficients are compared with values calculated from the critical data by the Berthelot equation. The results show two distinct classes of behaviour. Class I is shown by ethane, ethylene, n -hexane, cyclohexane, benzene, diethyl ether, ethyl chloride, chloroform and carbon tetrachloride, where the measured second virial coefficients are in agreement with the calculated values. Class II by acetaldehyde, acetone, acetonitrile, methyl alcohol, where the measured second virial coefficients are consistently very much higher than the calculated values. It is concluded that the vapours of polar substances for which the energy of attraction between molecules, due to dipole interaction or to hydrogen bonding, is larger than kT undergo dim erization. This view is supported by thermal conductivity data. The range of validity of the Berthelot equation for both non-polar and polar vapours is examined.

Measurements of the (p, ρ,T) properties and virial coefficients of pure water, methane,n-hexane,n-octane, benzene, and of their aqueous mixtures in the supercritical region

“…--, values calculated from square-well potential. (40) r, Kell et al; (41) (45) w · , Haar et al; (46) w, O'Connell and Prausnitz; (47) (57) +, Griskey and Canjar; (58,59) R, McGlashan and Potter; (22) w, Collings and Laughlin; (69) U, Lee and Edmister; (70) $, Pompe and Spurling. (71) calculated using the two potential functions.…”

Acetaldehyde adsorption and condensation on anatase TiO2: Influence of acetaldehyde dimerization

“…Alexander and Lambert measured the second virial coefficient for acetaldehyde and observed a significant deviation from the value obtained from the Berthelot equation [25], and concluded that the extra interaction was due to the formation of cyclic dimers. Later Wilkinson and co-workers contributed to the topic in the 1940s with similar measurements, as well as by providing a theoretical explanation for the mentioned behaviour of acetaldehyde and other polar gases [26]. Just a few recent studies have reported on acetaldehyde dimerization [27][28][29][30], and the only experimental data known to us is the study by Curtiss and Blander, who also calculated the enthalpy of dimerization for a number of hydrogen-bond-forming compounds, including acetaldehyde [27].…”

Intermolecular forces in gaseous ammonia and in ammonia – nonpolar gas mixtures

“…Lambert, et al (19,20) have shown that for a weakly associated gas the second virial coefficient is of the form ; given by Buckingham where B,,,, is the physical contribution (calculated from the intermolecular potential, eqs.…”