the Separation of the Isotopes of Mercury. 47 



Separation of the Mercury Isotopes using the Effusion 

 Method. 

 Fig. 5 represents an apparatus used for the separation of 

 the isotopes based on the method described on p. 34. The 



Fig-. 5. 



main quantity of the mercury vapour passes from the heated 

 bulb A into tube C cooled with ice, and only a fraction of 

 the vapour has the opportunity of entering the equally 

 cooled tube B by passing one of the numerous holes in a 

 platinum foil inserted in the glass tube at E. The diameter 

 of the platinum foil, as well as that of the glass tube, is 

 2 cm. and it has 1000 holes of 0'15 mm. diameter each. 

 The whole apparatus was thoroughly exhausted. 



As found by Kuudsen *, the rule of the molecular flow 

 through a narrow opening is only strictly valid when the 



* Ann. d. Physik, (4) xxviii. p. 999 (1909) ; xxix. p. 179 (1909). 



