An experimental check was made upon the theory given in Part I. Cracking catalyst was used as a solid and differently adsorbed tracer gases were used. In a two-dimensional fluidized bed bubbles were formed underneath a gauze cap, while solid flowed along the bubble at the corresponding bubble velocity. Tracer injections provided the value for the transfer coefficient. In three-dimensional beds of 18 and 90 cm dia. large traced gas bubbles were injected. Tracer concentration was detected at certain heights. From the decrease the transfer coefficient was calculated. In the 90 cm bed the transfer coefficient was also calculated from residence time distribution measurements when the dense phase was perfectly mixed. It shows, that the two-dimensional bubble confirms the theory. For three-dimensional bubbles the transfer is higher than theoretically predicted, especially when the dense phase is expanded.