Flow Type Apparatus for Measuring Vapor Pressures of High Boiling Compounds

Vapor pressures of high boiling compounds, such as heavy hydrocarbons, are important as fundamental data to predict or correlate vapor-liquid equilibria and solubilities in supercritical gases¹⁾, and to measure vapor pressures of high boiling compounds, in both liquid and solid states, a flow type apparatus was developed. A schematic diagram is shown in Fig. 1, and, details of an equilibrium cell (for a liquid sample) and a weighing trap are shown in Figs. 2 and 3, respectively. In principle^{1), 2)}, vapor pressures of a sample can be determined from Eqs. (1) to (6) by measuring gas phase volume (V'_g) and amount of sample trapped (w_s). To obtain reliable vapor pressure data, an optimum flow rate range should be carefully determined.^1),3) As shown in Fig. 4, one can find the range in which vapor pressures determined are independent of flow rate of carrier gas. The vapor pressure data of naphthalene thus obtained are shown in Table 1 and Fig. 5. Based on the error analysis, the present data are believed to be correct within 0.5% margin of error. As shown in Table 1 and Fig. 5, the present data coincide with the results of Camin and Rossini⁴⁾ (boiling point measurement), Fowler et al.⁵⁾ (static method), and Sato et al.³⁾ (flow type). From this, a flow type apparatus proposed in this work seems successful to measure vapor pressures of high boiling compounds in both liquid and solid states.