84 MODERN SCIENCE READER 



at which temperature it no longer obeys Boyle's law, but 

 contracts much more than would correspond to the latter. 

 A considerable excess of air should therefore be thrown 

 into the engine, in order actually to produce an amount of 

 cold as corresponding to theoretical calculation. 



This drawback is greatly diminished by raising the 

 initial temperature of expansion from 135 C. (211 

 F.) to 100 C. (148 F.) ; and in order to achieve this 

 result, Claude interposes between the temperature ex- 

 changer and the expansion engine an apparatus L, called 

 " liquef actor, " (Fig 2), into which part of the compressed 

 air is thrown after its passage through the exchanger. 



The air in L being under a pressure of about 40 atmos- 

 pheres will not liquefy as in Fig. 1 at 190 C. (310 

 F.), but at 140 C. (220 F.), which is the critical 

 temperature of air. The air expanded in the engine ac- 

 cordingly is first heated in L up to 140 C. (220 F.), 

 before entering the exchanger M, instead of being at a 

 temperature of 190 C. (310 P.), as in the original 

 apparatus. The air admitted into the engine thus is at a 

 somewhat higher temperature. This liquefying process, 

 which is called by the inventor "liquefaction under pres- 

 sure," can yield one liter of liquid air for each horse- 

 power hour. 



This remarkable process seems to have been recently imi- 

 tated by several constructors, such as, e. g., an engineer of 

 the New England Refrigerating Company, of Norwich, 

 Mr. Place, who in describing this process, states that: 



"The cold exhaust air from the engine is carried over 

 pipes containing air to be liquefied (in an opposite direc- 

 tion thereto) which is at a higher pressure of 600 pounds; 

 this exhaust air is then carried back over the incoming 

 compressed air being supplied to the engine, and cools that 

 cold air. . . ." In fact, this process is identical with the 

 one indicated by Claude in 1902. 



In order then to separate the oxygen from the nitrogen, 

 Claude uses a method based on the partial liquefaction of 



