An improved photographic technique was employed to obtain pictures, for bubble size analysis, in experiments conducted in the Unit AMk2G (511 cm ID, 305 cm tall glass column)] During these experiments measurements of the average gas hold-up were made at 200 and 265oc using FTk300 paraffin wax as the liquid medium and nitrogen as the gas. Additional experiments were performed adding oxygenates, stearyl alcohol and stearic acid, (5 - 10 % by weight) to the wax at a temperature of 265°C. The addition of oxygenates did not have a significant effect on the average gas hold'up.