82 MODERN SCIENCE READER 



Liquide, Ltd., at Paris, Lyons, Marseilles, and in Belgium 

 at Dugree near Liege, while in October new works will be 

 opened in Italy and Germany. 



In the Claude process for the liquefaction of air, the 

 expansion of compressed air with the production of recov- 

 erable external work is made use of, that is, expansion takes 

 place on the piston of a reciprocating engine. Though this 

 method, according to theory, gives far better yields than 

 that of expansion through a valve, many scientists previous 

 to Claude (such as Siemens, Solvay, Hampson) in vain 

 endeavored to carry out the expansion of compressed air 

 in an engine, and Linde even believed it to be utterly 

 impossible. 



There was, in fact, one great difficulty to be overcome in 

 this connection, viz., the lubrication of an engine at such 

 low temperatures that all lubricating substances would 

 have become frozen. Claude succeeded in eliminating this 

 difficulty by using light petroleum ethers, which at ordinary 

 temperatures are not lubricants, but acquire lubricating 

 properties as the temperature is getting very low. Claude 's 

 first successful experiments were officially announced to 

 the French Academy in 1902 by the well-known physicist, 

 Professor d'Arsonval. 



In Claude's original machine (see Fig. 1) the compressed 

 air was cooled in the inner tube of the exchanger J/, in 

 order then to be expanded in the engine, the liquefied 

 portion being collected at the end of the expansion in the 

 receptacle R,, while the unliquefied portion was allowed to 

 flow through the outer tube B of the exchanger M, thus 

 cooling the incoming compressed air. 



It is true that this original system failed to give really 

 satisfactory results, because of the many difficulties arising 

 from the liquefaction taking place in the cylinder itself; 

 as moreover liquefaction is effected at 190 C; (310 

 F.) at the end of expansion and under atmospheric pres- 

 sure, the air in this condition, after traversing the ex- 

 changer, reaches the engine at about 135 C. (211 F.), 



