The phenomenon of "mass transfer with chemical reaction" takes place whenever one phase is brought into contact with one or more other phases not in chemical equilibrium with it. This phenomenon has industrial, biological and physiological importance. In chemical process engineering, it is encountered in both separ­ ation processes and reaction engineering. In some cases, a chemical reaction may deliberately be employed for speeding up the rate of mass transfer and/or for increasing the capacity of the solvent; in other cases the multiphase reaction system is a part of the process with the specific aim of product formation. Finally, in some cases, for instance "distillation with chemical reaction", both objectives are involved. Although the subject is clearly a chemical engineering undertakin~, it requires often a good understanding of other subjects, such as chemistry and fluid mechanics etc., leading to publications in diversified areas. On the other har.d, the subject has always been a major field and one of the most fruitful for chemical engineers.