208 Liming and Dewar — Separation of the Least Volatile 



through the rubber cork which closed A, and from the top of 

 B a second tube, b, passed through the cork and on to the rest 

 of the apparatus. Each of these tubes had a stopcock, m and 

 n, and the end of tube a was open to the air. A wider tube 

 also passed through the cork of A and led to an air-pump, 

 whereby the pressure above the liquid air in A was reduced, 

 and the temperature of the liquid reduced by the consequent 

 evaporation. To keep the inner vessel, B, covered with 

 liquid, a fourth tube, r, passed through the cork, and its lower 

 end, furnished with a valve, p, which could be opened and 

 closed by the handle q, dipped into liquid air contained in the 

 vessel C. As the pressure above the liquid in A was less than 

 that of the atmosphere, on opening the valve p some of the 

 liquid air was forced through r into A by the pressure of the 

 atmosphere, and in this way the level of liquid in xi main- 

 tained at the required height. 



Since B was maintained at the temperature of liquid air 

 boiling at reduced pressure, the air it contained condensed on 

 its sides, and when the stopcock n was closed and m opened 

 more air passed in through the open end of a, and was in turn 

 condensed. In this way B could be filled completely with 

 liquid "air, the whole of the most volatile gases being retained 

 in solution in the liquid. 



The tube b, passing from the top *of B, was connected with 

 a three-way stopcock d, by which it could be put in communi- 

 cation with the closed vessel, I), or with the tube e, and by 

 which also D and e could be connected. The tube e passed 

 down nearly to the bottom of the vacuum-jacketed vessel E, 

 and out again through the cork ; and so on to a gauged, and 

 through a sparking tube g to a mercury pump F* The stop- 

 cock n being still closed, the whole of the apparatus between 

 n and the pump, including the vessel L), was exhausted, and 

 liquid hydrogen introduced into E. The three-way cock d 

 was then turned so as to connect b with _D, and close e, and 

 then n opened. B was thereby put in communication with D, 

 which was at a still lower temperature than B, and the gas 

 dissolved in the liquid in B, along with some of the most vola- 

 tile part of that liquid, distilled over, and the latter condensed 

 in a solid form in L). When a small fraction of the liquid in 

 B had thus distilled, the stopcock d was turned so as to close 

 the communication between B and b and open that between 

 D and e. Gas from D passed into the vacuous tubes, but in 

 so doing it had to pass through the portion of e which was 

 immersed in liquid hydrogen, so that condensible matter car- 

 ried forward by the stream of gas was frozen out. 



* The Sprengel in figure is simply diagrammatic. 



