Orthobaric liquid densities and dielectric constants of (methane+2-methyl-propane) and (methane+ n-butane) at low temperatures

Abstract

Measurements of the orthobaric liquid densities and dielectric constants of methane-rich (methane+2-methylpropane) and (methane+ n-butane) have been obtained at temperatures between 110 and 140 K. Densities were determined with a magnetic-suspension densimeter, while a concentric-cylinder capacitor was used for simultaneous measurements of dielectric constant. These measurements were part of an experimental program that has provided a consistent and comprehensive set of densities for the major components of liquefied natural gas (LNG) and their mixtures, which was used to develop mathematical models for the calculation or prediction of LNG densities. Along with the (methane+2-methylpropane) and (methane+ n-butane) experimental densities and dielectric constants, are presented experimental vapor pressures, as well as excess volumes, Clausius-Mossotti functions, and excess Clausius-Mossotti functions, derived from the densities and dielectric constants. Comparisons are shown between the excess volumes of the present work and those from independent measurement using an extended corresponding-states model that had been optimized to the results from this work. The total uncertainty of a single density measurement is approximately 0.1 per cent with a precision of a few parts in 10 4. Dielectric constants are estimated to be accurate to approximately 0.05 per cent. A brief description of the apparatus, experimental method, and procedures is also presented.