Estimate of the Vapor Pressure of Squalane at Approximately 293 K Using a Knudsen Cell Method

Abstract

I report the vapor pressure of squalane hydrocarbon (2,6,10,15,19,23-hexamethyltetracosane, C30H62) estimated from a statistical analysis of multiple weight loss measurements of Knudsen cells with orifice diameters of 4 and 8 mm exposed in vacuum for aggregated durations 5400 and 2400 h, respectively, at 293.61 ± 1.47 K. The estimated vapor pressure pv = (4.15 ± 0.17) × 10–6 Pa is more than a factor of 6 larger than the value of ∼6.5 × 10–7 Pa derived from estimates reported in the literature. Plausible systematic errors cannot account for this discrepancy, which suggests that the vapor pressure of squalane at temperatures near 293.61 K may be substantially higher than previously estimated. Empirical equations for the vapor pressure of squalane are proposed for the temperature range 293.61 K ≤ T ≤ 795.9 K.