232 



SCIENCE PROGRESS 



potash. After again remeasuring a spark is passed ; if necessary 

 oxygen is added, and the mixture again exploded. The gas is 

 treated with potash for the second time ; the contraction in this 

 case is due to carbon monoxide. From these series of measure- 

 ments the amounts of hydrogen, oxygen, and the oxides of 

 carbon are easily calculated. Finally, the gas is transferred 

 to a second test-tube containing a pellet of phosphorus, and 

 the excess of oxygen thus removed. The residue consists of 

 nitrogen and inert gases. 



TO PUMP 



Fig. 2. 



In examining these, advantage is taken of the fact, discovered 

 by Dewar, that charcoal cooled to the temperature of liquid air 

 absorbs nitrogen and the heavier inert gases. Neon and helium 

 are not absorbed. It is thus possible to separate them from 

 nitrogen and argon. The separation is carried out in the 

 apparatus shown in fig. 2. The gases are taken through the 

 inverted siphon into the burette b, the rest of the apparatus is 

 evacuated through the tap g connected to a mercury pump. 

 During this operation the bulb e containing charcoal is heated at 

 230 in quinoline vapour to free the charcoal from adsorbed gases, 

 and at the same time a current is passed through the spectrum 



