DIFFUSION OF HALOGENATED HYDROCARBONS IN HELIUM . EFFECT OF STRUCTURE ON COLLISION CROSS SECTIONS

Experimental binary gas-phase diffusion coefficients for some halogenated hydrocarbon compounds diffusing into helium have been determined utilizing the gas chromatography (GC) peak-broadening technique. Certain modifications are described which have improved the speed and accuracy of the technique. A critical discussion of the validity of the method is given. Based mainly on the acquired data, additional parameters have been determined for use in connection with the Fuller-Schettler-Giddings diffusion volume method for estimating binary diffusion coefficients. The relationship between effective collision cross sections and various molecular shape and structural features is discussed.