Gaseous Mixtures

Gaseous Mixtures.— The thermodynamic properties of a system in the dilute gaseous state are a potentially fruitful source of information concerning the intermolecular pair potential, (r). Equation (1) is an exact relation for spherically symmetric molecules between u(r) and B, the second virial coefficient. 

However, because of the relative insensitivity of B(T) to (r) it is usually impossible to arrive at a unique u(r) on the basis of second virial coefficients alone and other data such as gas viscosities or collision cross-sections determined from molecular beam experiments must be utilized to define u(r) unequivocally. 

The measurements of Douslin et al. are particularly valuable because the virial coefficients of the two pure substances Bn and B22 and the interaction virial coefficient B were measured over such a range of temperature that it was possible to make a direct determination of the Boyle-point parameters and F = (rdi5/dr)T=TB. Bn, B22, and B12 were found to follow the same theorem of corresponding states when T and F were used as the reduction parameters, whereas this was not so when the more usual critical parameters, T and F were employed. The experimental values of T and F are given in Table 2 together with the values calculated by assuming the Lorentz-Berthelot combining rules  

Equations (2) and (3) are directly equivalent to the Lorentz-Berthelot rules in their more familiar form using e and a, the well depth and collision diameter associated with the intermolecular potential (r)  

Also shown in Table 2 is the value of Tf estimated by assuming the Hudson and McCoubrey combining rule  

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For precise measurements, diere is a slight correction for the effect of the slightly different pressure on the chemical potentials of the solid or of the components of the solution. More important, corrections must be made for the non-ideality of the pure gas and of the gaseous mixture. With these corrections, equation (A2.1.60) can be verified within experimental error. 

To proceed fiirther, to evaluate the standard free energy AG , we need infonnation (experimental or theoretical) about the particular reaction. One source of infonnation is the equilibrium constant for a chemical reaction involving gases. Previous sections have shown how the chemical potential for a species in a gaseous mixture or in a dilute solution (and the corresponding activities) can be defined and measured. Thus, if one can detennine (by some kind of analysis)... 

JiVith ammoniacal or hydrochloric acid solution of copper(I) chloride, carbon monoxide forms the addition compound CuCl. CO. 2H2O. This reaction can be used to quantitatively remove carbon monoxide from gaseous mixtures. 

So little systematic information is available about transport in liquids, or strongly non-ideal gaseous mixtures, that attention will be limited throughout to the behavior of ideal gas mixtures. It is not intende thereby, to minimize the importance of non-ideal behavior in practice. 

Now the force per unit volume exerted on the porous medium by the pressure gradient in the gas is -grad p, where p, as distinct from is the physical pressure of the gaseous mixture. This is the force which must be balanced in our model by the external forces acting on the dust particles, so... 

The differential material balances contain a large number of physical parameters describing the structure of the porous medium, the physical properties of the gaseous mixture diffusing through it, the kinetics of the chemical reaction and the composition and pressure of the reactant mixture outside the pellet. In such circumstances it Is always valuable to assemble the physical parameters into a smaller number of Independent dimensionless groups, and this Is best done by writing the balance equations themselves in dimensionless form. The relevant equations are (11.20), (11.21), (11.22), (11.23), (11.16) and the expression (11.27) for the effectiveness factor. 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

For condensed phases is used, and for gaseous mixtures y may be used. 

Plasma consists of a gaseous mixture of neutral species, ions, and electrons. The charged species are in approximately equal concentrations. 

Figure 8.25 shows the AXn,m. ii,iii Auger spectrum of a gaseous mixture of SFe, SO2 and OCS, all clearly resolved. The three intense peaks are due to sulphur in a >2 core state, but there are three weak peaks due to a core state also. The S 2p X-ray photoelectron spectrum of a mixture of the same gases is shown for comparison, each of the three doublets being due to sulphur in a 1/2 or 3/2 core state. 

Figure 8.25 (a) The ( 2 Xq) Auger spectrum of sulphur in a gaseous mixture... 

Oxidation. Acrolein is readily oxidized to acryUc acid, [79-10-7] by passing a gaseous mixture of acrolein, air, and steam over a catalyst... 

Applications in Oil and Gas Production. AMP is useful for removing CO2 from gaseous mixtures (23). It also has been utilized in tertiary oil recovery to enhance removal of petroleum from marginal wells (24). 

Hypochlorous acid reacts similarly to CI2O and cannot be distinguished from CI2O by wet analysis. Gaseous mixtures of CI2, CI2O, and HOCl can be analyzed by mass spectrometry (66,67), by in (68), or by uv spectrophotometry (9,66,69). Gas chromatography can be used to analyze mixtures of air, CI2, and CI2O (54). 

In the gas phase, methylene chloride reacts with nitrogen dioxide at 270°C to yield a gaseous mixture consisting mainly of carbon monoxide, nitric oxide, and hydrogen chloride (8). 

Many polymer films, eg, polyethylene and polyacrylonitrile, are permeable to carbon tetrachloride vapor (1). Carbon tetrachloride vapor affects the explosion limits of several gaseous mixtures, eg, air-hydrogen and air-methane. The extinctive effect that carbon tetrachloride has on a flame, mainly because of its cooling action, is derived from its high thermal capacity (2). 

Modem plants manufacture chlorosulfuric acid by direct union of equimolar quantities of sulfur trioxide and dry hydrogen chloride gas. The reaction takes place spontaneously with evolution of a large quantity of heat. Heat removal is necessary to maintain the temperature at 50—80°C and thus minimize unwanted side reactions. The sulfur trioxide may be in the form of 100% Hquid or gas, as obtained from boiling oleum, ie, fuming sulfuric acid, or may be present as a dilute gaseous mixture as obtained direcdy from a contact sulfuric acid plant (24). The hydrogen chloride gas can be in the form of 100% gas or in a diluted form. 

S. C. Sharma, "Equilibrium Water Content of Gaseous Mixtures," Ph.D. dissertation. University of Oklahoma, Norman, 1969. Available from University Microfilms, Ann Arbor, Mich., order 69-8601. 

For prediction of the vapor viscosity of gaseous mixtures of hydi ocai bons and nonhydixjcai bon gases at low pressures below a 7, of 0.6, the method of Bromley and Wilke is recommended. 

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