Abstract
The gaseous diffusion coefficients of dichloromethane (CH2Cl2), trichloromethane (CHCl3) and tetrachloromethane (CCl4) into dry air, nitrogen and oxygen have been measured in the temperature range 318-453 K and at atmospheric pressure by the use of the Taylor dispersion method. For dichloromethane, trichloromethane and tetrachloromethane, the diffusion coefficients do not vary in practice on substituting pure nitrogen or oxygen for dry air. The diffusion coefficients decrease with increasing molecular weight and those for trichloromethane and tetrachloromethane are systematically smaller than those for dichloromethane by about 14 and 25%, respectively. The present results can be reproduced well by the functional form D = ATB, where D(cm2s-1) is the diffusion coefficient at 101.325 kPa (1 atm) and T(K) is the absolute temperature. The constants A and B are as follows: dichloromethane-(air, nitrogen, oxygen), A = 8.67×10-6, B = 1.66; trichloromethane-(air, nitrogen, oxygen), A = 7.90×10-6, B = 1.65; tetrachloromethane-(air, nitrogen, oxygen), A = 9.36×10-6, B = 1.60.
