Vapor Pressure of Heptane from the Triple Point to the Critical Point

We have used a metal ebulliometer to make measurements of the vapor pressures of heptane. Measurements spanned the temperature range from 335 K to 503 K, and measured pressures ranged from 30 kPa to 1597 kPa. The sample purity was determined by chromatographic analysis, and the measured pressures were adjusted for the presence of the impurities found. The adjusted results were found to be in good agreement with the best available data from the literature, and a reliable vapor pressure curve could be established for temperatures up to the critical point (540.13 K). We have also used thermodynamic calculations and published thermal data to extend the vapor pressures down to the triple point (182.603 K). We estimate that our vapor pressure curve has an uncertainty of 0.2% to 0.3% in the vicinity of the triple point, decreasing to 0.03% to 0.05% in the range 300 K to 400 K, and increasing to about 0.1% at 500 K. The calculated critical pressure was found to be (2739.7 ± 2.5(1σ)) kPa.