ABSTRACT
Diffusion also plays a major role in peak broadening in chromatography, and accurate values of diffusion coefficients are often necessary in the testing of chromatographic theory. This chapter illustrates the various experimental methods for measuring diffusion coefficients by gas chromatography. It reviews the literature concerning the measurement of gas-gas and gas-liquid vapor binary diffusion coefficients by methods based on the chromatographic broadening technique. One of the problems associated with diffusion-coefficient measurement is the effect of finite injection volume, detector volume, and dead volume due to connecting tubing. The two-bulb apparatus developed by E. P. Ney and F. C. Armstead is essentially an improvement of the closed-tube method. J. Stefan developed the evaporation-tube method for measuring the diffusion coefficients of liquid vapor-gas mixtures. The point-source method of A. A. Westenberg and R. E. Walker is very similar in principle to the gas-chromatography method, except that the tracer is continuously steaming into the flowing carrier.
