Comments on the theory for separation of isotopic gas-mixture components flowing through a porous barrier

In the theory of Present and Bethune for separation of gas mixtures flowing through a porous barrier, the pores are long capillaries, cylindrical and of circular cross section, and the reflection of the gas molecules against the walls is supposed to follow Knudsen's law. Using, for binary mixtures, some methods already known for simple gases, we try to derive here similar separation theories for porous barriers whose pores may be short, tortuous and of various shapes of cross section, and where the reflection of the molecules may deviate from the usual cosine law. (author)