A study of the two-bulb method for measuring diffusion coefficients of binary gas mixtures

The concentration dependences of the binary diffusion coefficients of the systems He-Ar and He-O2 are reported at 300 K and 1 atm pressure. Two independent sets of data, obtained with a two-bulb cell and a shearing-cell of Loschmidt design, agree within the error of measurement. The data for the two-bulb cell were obtained at pressures where Knudsen effects are important. It was found necessary to improve the extrapolation procedure of van Heijningen et al. by using the results of the dusty-gas model as described by Mason et al.