A version of the Wicke-Kallenbach diffusion cell that utilizes the validity of Graham's law was used for counter-current diffusion measurements. Diffusion in binary and ternary inert gas systems (consisting of hydrogen, helium, nitrogen, argon) was followed via determination of net volumetric diffusion fluxes. In agreement with Graham's law these fluxes are significantly influenced by the composition of gases in diffusion cell compartments. Fitting of experimental data to the Mean Transport-Pore Model provides model parameters (transport parameters) that are independent of the gas kind and composition. Ternary diffusion extends the volume of experimental information and the confidence region of transport parameters shrinks significantly. The internal consistency of diffusion data verifies the validity of the multicomponent version of Graham's law.