441 



V 



vapour; accordingly the relation - characteristic of the diflfiisioii in 



Ö 



a flowing gas is not affected by small fluctuations in the vapour 

 density. In order to prevejit condensation of the water vapour 

 against the walls, the whole apparatus is enclosed in a box, in 

 which the air is heated a few degrees above the temperature in IF. 



The same degree of the separation is obtained by the first and 

 the second method. As regards the quantity obtained the second 

 method however, is considerably better. Only when it is required to 

 separate small quantities, the former method is preferable, as in 

 the second method a certain minimum quantity is required for the 

 circulation. 



It is of importance to consider whether our method of the diffusion 

 in a gas current is more efficient with regard to the separation of 

 isotopes than the methods used up to now. This new method is 

 no doubt superior to the usual way of separation by diffusion. It 

 is, however, possible, that when we apply this method to gases 

 with diffusion-constants differing as little as they do for isotopes, 

 small irregularities in the current may have much greater disturbing 

 influence than in neon-helium mixtmes. Nor can it, of course, 

 be expected that a mixture of isotopes should be completely separated 

 by a single process of diffusion, for such a process, supposing it 

 be possible in principle, would require a very long time, as can 

 be calcidated from the above given formulae. On the other hand, 

 e.g. in neon, a change in the ratio of mixing of the isotopes of 

 about 30 7o could be expected as the result of one process of 

 diffusion, so that it might be expected that a fairly far advanced 

 separation can be obtained after not too many repetitions. It is 

 not our intention to use the apparatus described above for the 

 separation of isotopes, as it must undoubtedly be possible to 

 construct apparatus on the same principle, working considerably 

 more rapidly. 



Eindhoven, 1922. Physical Laboratory of the 



•'jVI V. Philips' Gloeilampenf abrieken." 

 {Philips' Incandescent Lamp Works). 



