AbstractFrom time to time, A.I.Ch.E. Journal presents translations of certain technical articles written by our Japanese colleagues in their own language. These translations are made by Kenzi Etani, who received his B.S. in chemical engineering in 1953 at the Tokyo Institute of Technology and his M.S. in 1955 at M.I.T. He is associated with Stone & Webster and is an associate member of American Institute of Chemical Engineers. He is also a member of the Society of Chemical Engineers, Japan, and the Japan Oil Chemists' Society. His offer to help break down the language barrier is acknowledged.Abstracts, notation, literature cited, tables, and figure captions not published here appear in English in the original paper. No figure will be reproduced in these translations.The following article was published in Chemical Engineering (Japan), 21, pages 17–25 (1957).