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MODERN SCIENCE READER 



air. Although so competent an authority as Sir J. Dewar 

 emphatically denied the possibility of partially liquefy- 

 ing air, maintaining that the oxygen would come down 

 together with the whole of the nitrogen, Claude succeeded 

 in experimentally demonstrating that his idea could very 

 well be carried out in practice, a liquid rich in oxygen 

 being at first given out from air. In Claude's process, this 

 partial liquefaction is combined with what is called the 

 "backward return" of the liquid portions, this additional 

 factor being necessary to allow of a satisfactory separation 

 of the air in course of liquefaction. 



M 



F IG . 3. SYSTEM OF COOLING AND LIQUEFYING COMPRESSED AIR 



In Fig. 3 the compressed air cooled in the exchangers 

 M and N, after entering the apparatus in T, is liquefied 

 gradually in the set of tubes F surrounded by liquid air, 

 the first drops containing about 48 per cent, of oxygen. 



While the remaining gas, which is a little poorer in 

 oxygen than air, rises higher up in the tubes, a liquid comes 

 off containing less than 48 per cent, of oxygen. However, 

 as soon as some liquid is produced in the tubes, it, owing 



