PKODUCTION OF OXYGEN 



87 



to its weight, returns backward in an opposite direction to 

 the ascending gases and in contact with them, so that part 

 of the oxygen of those gases is liquefied, replacing a cor- 

 responding amount of liquid nitrogen, which is vaporized. 



The same process is repeated throughout the length of 

 the tubes, and allows a liquid to be obtained holding forty- 

 eight per cent, of oxygen and comprising the whole of the 

 oxygen of the air, leaving on the other hand pure gaseous 

 nitrogen. 



In spite of these remarkable 

 results, the partial liquefaction 

 conducted under the conditions 

 described still proved inade- 

 quate for manufacturing pure 

 oxygen. The latter was ob- 

 tained only by combining the 

 principle of liquefaction as 

 above described with the rectify- 

 ing process used for many years 

 in the distilling industries. 

 1 Fig. 4 shows the apparatus 

 constructed for this purpose. 

 The cold compressed air at A 

 enters the tubes F, and is par- 

 tially liquefied in the latter. 

 The liquid thus formed returns 

 in an opposite direction to the 

 ascending gases, and finally 

 yields a liquid containing about 

 forty-eight per cent, of oxygen, 

 while pure gaseous nitrogen 

 comes out at the top of the tubes Fl(J 4> J^RATUS FOR SEP- 

 F, in order then to be liquefied ABATING ATMOSPHERIC AIR 

 in the tubes F'. The liquid rich 

 in oxygen collected at C, owing 

 to its pressure, is poured out in the central part of the 

 column, and rectifies the ascending gases up to a percentage 



-f 

 -V 



INTO PURE 

 NITROGEN 



OXYGEN AND 



