Compression-Factor Measurements on Methane, Carbon Dioxide, and (Methane + Carbon Dioxide) using a Weighing Method

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Compression factors Z have been measured using the direct method of measuring mass, volume, temperature, and pressure. It is demonstrated that using a high-sensitivity mass comparator results can be obtained with accuracies comparable to more demanding traditional indirect methods. Z values for {(1 − y)CH4 + yCO2} with y= 0, 0.25, 0.5, 0.75, and 1 are reported at temperatures of 303.15, 313.15, 323.15, and 333.15 K. The results are found to be in agreement with the “GERG” equation of state for natural-gas components. Second and third coefficients derived from the results have been compared with literature values and with predictions of the Tsonopoulos equation using k12 values estimated from critical-point measurements.