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Ethylene Burnett

Values of the second virial coefficient of ethylene for temperatures between 0° and 175°C have been determined to an estimated accuracy of 0.2 cm3/mol or less from low-pressure Burnett PVT measurements. Our values, from —167 to —52 cm3/mol, agree within an average of 0.2 cm3/mol with those recently obtained by Douslin and Harrison from a distinctly different experiment. This close agreement reflects the current state of the art for the determination of second virial coefficient values. The data and error analysis of the Burnett method are discussed. [Pg.287]

The results themselves have a subtlety associated with their interpretation owing to the presence of the volume-ratio parameter and, optionally, the initial density parameter. The Burnett equations have more flexibility to fit Burnett data than only a density series to PVT data. The statistical uncertainties reflect the quality of the experimental data relative to the particular model used to describe the experiment. The estimation of accuracy for Burnett results is necessarily somewhat subjective since the effect of systematic errors on parameter values is not explicit in nonlinear equations, such as the Burnett equations. Accuracy, however, can be estimated from a study of the effects of systematic errors in computer model calculations and from the magnitude of the change in the volume-ratio value determined with nonideal and nearly ideal gases. For these reasons, we include such information along with our virial coefficient results for ethylene. [Pg.292]

The apparatus used in this experiment is basically the same as the Burnett PVT apparatus shown in Figure 2 and described in our earlier publications (12,13). The only noteworthy modification stems from a need for refinishing the surfaces exposed to the sample gas because of a chemical reaction between the ethylene sample and the transducer backing surface during our first ethylene measurements. In this section we describe the apparatus, discuss the nature of the reaction, and report the purity analyses for the gases—ethylene and helium—used in this experiment. [Pg.293]

Multiple sets of Burnett data were obtained for each isotherm—three sets for ethylene and two sets for helium. Each set consisted of data from a series of four consecutive expansions from the highest to the lowest pressure compatible with our optimum accuracy and precision. The initial pressure for each set was selected so as to intersperse the data from all of the sets over the entire pressure range of interest, 0.3 MPa to 3.7 MPa. Consistent with the extent of the nonideal behavior of the gas, the density-series generalized equation was applied to the ethylene data and the pressure-series generalized equation was applied to the helium data. The parameters in the resulting overdetermined sets of equations then were evaluated using the least-squares constraint. [Pg.296]

The effects of systematic errors are best studied by analyses of accurate Burnett data with superimposed simulated errors. For a relative pressure offset of 0.003%, which is comparable with the accuracy of piston gauges, the ethylene second virial coefficient of —167 cm3/mol changes only by 0.02 cm3/mol. Thus, this type of error is largely cancelled in the Burnett method. An offset in N of 11 ppm, which is comparable with the N variation we expect, changes the same second virial coefficient by 0.1 cm3/mol. Errors resulting from truncation of the series... [Pg.297]

Figure 4. Comparison of Ethylene Burnett results for N treated as a parameter to those for N treated as a constant... Figure 4. Comparison of Ethylene Burnett results for N treated as a parameter to those for N treated as a constant...
In Figure 5, we present a comparison of our preferred values for the ethylene second virial coefficient with comparable state of the art results obtained by Douslin and Harrison (2). The experimental method and data analysis used by Douslin are independent from ours. In Douslin s experiment, all of the variables required for the calculation of the compressibility factor are measured, whereas in the Burnett method only two variables are measured. Aslo, in this experiment the same sample of gas is retained for the entire experiment in the Burnett isothermal method, the sample is changed for each sequence of measurements. Furthermore,... [Pg.303]

Ito et have studied relaxation in poly(ethylene sebacate) and poly(deca-methylene-l,16-hexadecane dicarboxylate) using the solid echo technique a and relaxations consistent with dielectric data were observed, the jS process being associated with the ester group. In poly(dimethylsiIoxane), Burnett et al. observed two spin-lattice relaxation time minima at <85 and 200 K and a discontinuity in Ti at 230 K. The low temperature minimum was assigned to methyl rotation, the high temperature minimum to a chain stretching and oscillational mode, and the discontinuity to melting. [Pg.245]


See other pages where Ethylene Burnett is mentioned: [Pg.145]    [Pg.454]    [Pg.289]    [Pg.297]    [Pg.300]   
See also in sourсe #XX -- [ Pg.287 , Pg.296 , Pg.299 ]




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