Measurement of the Diffusion Coefficients of Organic Vapor into Air by the Stefan Method (3rd Report Measurement on the CFC113-Air and Trichloromethane-Air Systems)

Abstract

Using the Stefan method, the gaseous diffusion coefficients of CFC113 (molecular weight 187.4) and trichloromethane (molecular weight 119.4) into dry air were measured at atmospheric pressure. The measurement was carried out at 310.2 K (37 ℃) for CFC113 (vapor pressure 0.070 MPa) and at 324.2 K (51 ℃) for trichloromethane (vapor pressure 0.072 MPa). The diffusion path lengths L(≅ 80×10^-3 m, 120×10^-3 m, 160×10^-3 m) and the air flow rates Q (3.3×10^-6 m³s^-1-100×10^-6 m³s^-1 (200 cm³min^-1-6000 cm³min^-1)) were systematically changed as in our previous reports. The vapor pressures of the organic vapors in this report are nearly equal to 0.071 MPa for diethyl ether (molechular weight 74.1) at 298.2 K (25 ℃), studied in our second report. But the air flow rates Q suitable to the measurement in this study were found to be higher than that for diethyl ether. This implies that Q suitable to the measurement may depend on the molecular mass of the origanic vapor. The present experimental values of D for CFC113 and trichloromethane into air agree well with the extrapolation of our experimental data obtained by the Taylor dispersion method to lower temperature, as in the case of the results for diethyl ether reported in our previous reports.