Tricritical phenomena in quasi-binary mixtures. V. New measurements on ternary methane systems

Abstract

Phase equilibria have been studied in ternary mixtures of methane with 2,2- and 2,3-dimethylbutane near the tricritical point. The quasi-binary approximation allows the path to the tricritical point to be defined experimentally, making it possible to study the details of the phase behavior as the tricritical point is approached. The decrease in the differences in temperature and pressure between the upper and lower critical end points is consistent with the asymptotic classical theory of tricritical phenomena; an extended classical theory is necessary to account for the shape of the coexistence curves.

Theoretical Examination of the Global Fluid Phase Behavior and Critical Phenomena in Carbon Dioxide +n-Alkane Binary Mixtures

“…The global phase diagram shown in Figure 9 describing the continuous transitions in types of phase behavior for CO 2 + n-alkane binary mixtures is similar to those presented previously by Scott and van Konynenburg 8,9 and Scott and co-workers. [151][152][153][154][155] In the first case, the critical end-point properties are plotted against the dispersive energy ratio (a 22 /a 11 ) parameter of the van der Waals equation of state which accounts for the asymmetry between the components of the mixture (see Figure 3 of the work of Scott and Konynenbrug 8 ). In the second case, a similar plot is used to study the tricritical behavior of pseudobinary mixtures of n-alkanes.…”

Critical behavior and partial miscibility phenomena in binary mixtures of hydrocarbons by the statistical associating fluid theory

“…1,2 Knowledge of the phase diagrams of binary mixtures of hydrocarbons allows one to select, in a systematic way, which ternary mixtures will exhibit such tricritical behavior. [3][4][5][6][7][8][9][10][11] In essence, what one looks for is a transition region in the phase diagram of two very similar binary mixtures in which there is a change from complete miscibility to partial miscibility ͑i.e., presence of a LLG three-phase line close to the critical point of the more volatile component͒, following the Rowlinson nomenclature. [12][13][14] There are several hydrocarbon mixtures exhibiting such behavior: methane(1) ϩn-pentane(2) and methane͑1͒ϩ2,2-dimethylbutane͑2͒ are typical examples of type-II systems in the Scott-Konynenburg classification, 2,15,16 characterized by the absence of the LLG line close to the critical point of methane.…”

Photorotamerization of methyl salicylate and related compounds in cryogenic matrixes

“…The UV emission, with its distinct lifetime and temperature-dependent intensity,3 has been attributed to fluorescence of a stable rotamer for which the structure MS-E (below) was proposed. 4 There is, however, scant spectral evidence supporting the rotamer structure; direct spectroscopic observation of MS-E has been limited to weak vibrational features arising from its equilibrium population (~1%) present in thin-film IR spectra at room temperature,4 and high-resolution emission spectra of jetcooled gas-phase samples.5 Previous attempts to trap the MS-E rotamer by irradiation in Ar, N2 and Xe matrices were unsuccessful. 6 In this paper, we report the photolytic behavior of MS-C isolated at 12 K in SF6 and Xe matrices.…”

“…Figure4. FTIR difference spectrum of SAM-C (negative features) and its photolysis product SAM-F (positive features) in 12 K Ar matrix after 1 h 45 min laser irradiation (5 mW, 320 nm).…”