Diafytic Separation of Gases by Colloid Septa. 409 



gas for some time, but with a negative result. The absorbed 

 hydrogen may be too easily dissipated, owing to its extreme vo- 

 latility. 



Dialytic separation of Oxygen from Atmospheric Air, (1) by 

 means of other gases, (2) by means of a vacuum. 



1 . A balloon of rubber filled with hydrogen and exposed to the 

 atmosphere, gradually loses the former gas, which is finally re- 

 placed by a considerably smaller volume of air, presenting a de- 

 ceptive resemblance to the diffusion of hydrogen gas into air. 

 When the progress of the entrance of air was observed at differ- 

 ent stages of the exchange, it appeared that after three hours, 

 when the balloon had fallen from 150 to 128 millims. in diameter, 

 the composition of its contents was — • 



Oxygen . . . 8-98 41'6 

 Nitrogen . . . 12-60 58'4 

 Hydrogen . . 78-42 



100-00 100-0 



Setting aside therefore the hydrogen still remaining, the bal- 

 loon now contained a portion of a mixture of oxygen and nitro- 

 gen in the proportion of 41*6 volumes of the former to 58*4 

 volumes of the latter. This was the largest proportion of oxygen 

 to the nitrogen observed ; for the former gas has a tendency to 

 flow back again to the external atmosphere when the hydrogen 

 becomes small in volume ; and the proportion of oxygen becomes 

 eventually no higher than 21 per cent, of the whole gases remain- 

 ing in the balloon, including the hydrogen. Thus after six 

 hours the proportion of oxygen was 33*63 to nitrogen 66'37 vo- 

 lumes, and after twenty-four hours oxygen 26'48 to nitrogen 

 73*52 volumes, the hydrogen constantly diminishing at the same 

 time. 



The entrance by infiltration of atmospheric air into a balloon 

 of rubber inflated with carbonic acid gas brings us still nearer to 

 a practical dialytic separation, as the carbonic acid can be with- 

 drawn entirely by means of caustic alkali, after a certain time 

 has elapsed, and the infiltered air enriched with oxygen be dealt 

 with by itself. A balloon containing carbonic acid, when placed 

 in the atmosphere, was reduced in four hours from 160 to 90 

 millims. in diameter, and it had now acquired 199 cub. centims. 

 of gas not dissolved by alkali. This gas was capable of reviving 

 the combustion of wood burning without flame, and was found 

 to consist of 



Oxygen . . . . 37" 1 vols. 

 Nitrogen .... 62'9 „ 



100-0 



