Isochoric (p, V, T) measurements have been made on three mixtures of nitrogen and methane (0.29N2 + 0.71CH4), (0.50N2 + 0.50CH4), and (0.68N2 + 0.32CH4) at densities of 1 to 6 mol·dm−3. The three isochores for each mixture cover a temperature range from approximately 150 to 320 K up to a maximum pressure of 16 MPa. Comparisons with other experimental results and with values calculated from an extended corresponding-states model are discussed.

Three mathematical models of the equation of state for liquid mixtures simulating liquefied natural gas (LNG) are discussed and compared. The adjustable parameters for each model have been optimized using the same set of experimental data, consisting of over 280 new (p, V, T, x) points taken at the National Bureau of Standards in Boulder, Colorado. It is estimated that each of the models will predict LNG densities over its range of validity to within 0.1 per cent of the true values, given the pressure, temperature, and composition of the mixture. Deviation plots and a detailed performance evaluation are given for each model. The range of validity varies slightly among the models but in general the range of the study included the saturated liquid from 90 to 135 K.

Speeds of sound for nitrogen gas have been measured at pressures from 0.03 to 1.5 MPa on 16 isotherms from 80 to 350 K. Measurements were made in a fixed-path acoustic cavity using variable-frequency electrostatic transducers operating between 1 and 30 kHz. Correction for boundary-layer effects were made using existing values of thermodynamic properties.

The objectives are the determination of comprehensive accurate thermophysical properties data and predictive calculation methods for the major pure components (methane, ethane, propane, butanes, and nitrogen) and selected mixtures of liquefied natural gas and hydrocarbon mixtures at temperatures between 80 K and 320 K and at pressures up to 35 MPa (5000 psi).