271 



XI On an Apparatus for collecting the Gases from 



Water and other Liquids^ and its Application in 

 general Chemical Analysis. 



By Robert Angus Smith, Ph.D., F.C.S. 



[Read March OM, 1855.] 



There never has been, to my knowledge, a suitable 

 apparatus for collecting the gases from water. These 

 gases have been collected, but the widely different results 

 of Dal ton and Saussure shew how imperfect have been 

 the methods used. The apparatus, not till lately altered^ 

 as far as 1 can understand the description, was simply a 

 retort filled both in the neck and bulb; when heated the 

 water would of course first come from the neck, this being 

 inserted under a receiver, over mercury, would cause first a 

 certain amount of water to rise in the receiver. After some 

 time ebullition would begin, and steam and gas would 

 escape together. The method is in a high degree unplea- 

 sant to work with, and the loss is apt to be great, the 

 water that comes over being suflBcient to absorb a consider- 

 able amount of the gas. Again, there must be so much 

 evaporated that the steam itself, when condensed, will form 

 a large portion of the water that comes over, and the result 

 obtained must, in a great measure, be the difference between 

 the quantity of air absorbed by the water during a long 

 space of time, and the quantity absorbed in a short time by 

 a smaller quantity of water. This absorption must, of neces- 

 sity, take place when the water over the mercury has cooled. 



