402 



Professor Sir James Dewar 



[Jan. IS, 



at once formed a film and pushed it along to the desired position. 

 A was then closed and the film left to become black. Meanwhile a 

 small current of hydrogen was continued through B and C to 

 prevent any subsequent disturbance of the film, such as by an 

 alteration of temperature. 



O 5 10 TIME 15 MlNUTLo 20 



Hydrogen- Oxygen Diffusion r„«ouc„ Black Film 



Fig. 



Before starting the air or oxygen current through B and C the 

 film was lubricated by a slow complete revolution of the vessel, 

 whereby the small amount of liquid inside flowed all round the 

 walls. This caused some diminution of the black area, which was 

 measured and allowed for. Dui'ing the suljsequent diffusion the 



