Measurement of the Diffusion Coefficients of Organic Vapor into Air by the Stefan Method : (2nd Report Measurement on the Diethyl Ether - Air System at 298 K)

Abstract

Using the apparatus for the measurement of gaseous diffusion coefficients D by the Stefan method described in the first report, the diffusion coefficient of diethyl ether vapor into dry air was measured at 298.15 K (25°C)and at atmospheric pressure. The diffusion path lengths L(≅ 80×10^-3 m, 120×10^-3 m, 160×10^-3 m) and the air flow rates Q (0.8×10^-6 m³s^-1 -42×10^-6 m³s^-1 (50 cm³min^-1-2500 cm³min^-1)) were systematically changed as in the first report. A loose polyester cotton plug was inserted into the horizontal tubing just upstream of the mouth of the evaporation tube to straighten air flow. The present results were compared with those in the first report obtained at 303.15 K (30°C). The air flow rate Q suitable to the measurement (5×10^-6 m³s^-1 -16×10^-6 m³s^-1 (300 cm³min-1000 cm³min^-1)) was found to be lower than that for 303.15 K. The range of the air flow rate Q suitable to the measurement was narrowed with increasing diffusion path length L. Both the present experimental value (D = 0.091×10^-4 m²s^-1) and that at 303.15 K in the first report agree well with the extrapolation of our experimental data obtained by the Taylor dispersion method to lower temperature.