To achieve a complete resolution system of organic chlorinated compounds, the gas absorption of organic chlorinated compound gas into a molten salt has been considered. In this process the dispersion of gas bubbles in molten salts has played an important role for the efficient mass and heat transfers. The common dispersion method is blowing the gas bubbles through nozzles or orifices submerged in liquids. Much research has been done on bubble formation from upward nozzles or orifices in liquids, while little has been known about the bubble formation from downward nozzles. The purpose of the present study is to investigate the effects of nozzle shape and operating parameters on bubble formation mechanism from the vertically downward nozzle. As a result, the bubble formation and the bubble size are influenced by the edge angle of nozzle, inner and outer diameters of nozzle, and gas flow rate, whereas the gas chamber volume hardly influences on the bubble size. (c) 2006 Elsevier Ltd. All rights reserved.