The experimental determination of the volumetric properties and virial coefficients of the methane‐ethylene system

Abstract

For the case when x # 0, the substitution of Equation (A8) into Equation ( A 6 ) yieldsFurthermore, this equation can be written as Without loss of generality the arbitrary constant, C1, can be set equal to one. Then, the substitution of Equation (A8) into Equation (A4) with the relation, Equation (A5), gives the similarity transformation, Equation ( 7 ) , and Equation (A10) becomes Equation ( 8 ) . Similarly, the transformed boundary conditions for Equations (A2) and ( A 3 ) are those given in Equations ( 9 ) Volumetric (or compressibility factor) data are of industrial interest in process design calculations. The data are also of value in the calculation of derived thermodynamic quantities and in the further development of generalized methods for estimating thermodynamic properties from a minimum of direct data.In the past, several experimental facilities have been developed for determining compressibility factors of mixtures or pure components along isochoric (constant density) paths. The apparatus of Goodwin ( 7 ) , Michels (16, 2 0 ) , and Solbrig and Ellington ( 2 8 ) are of the isochoric type. In principle the compressibility factors for a constant composition system become established with the simultaneous knowledge of the three quantities pressure, temperature, and density. At selected points along an isochoric path the pressure and temperature are directly measured, and the data thus consist of a series of P-T points at constant density. The value of the density may be determined by separate measurement of the mass and volume quantities or, alternately, the density may be determined from the previously measured compressibility factors of the sample at a reference temperature.In the apparatus described herein, the density of the sample is determined from the compressibility factors along the reference isotherm (77°F.). The isotherm is independently determined using a Burnett type of apparatus ( 3 ) .The methane-ethylene binary system was selected for this study. The compressibility factors of the methane system have been extensively reported from -274 to 650°F.