ATTAINMENT OF VERY LOW TEMPERATURES. 



a quantity ten percent greater than that calculated on the assumption 



that the thermal capacities of 

 the compressed and expanded 

 hydrogen are the same. This 

 difference is insignificant and 

 has no eft'ect on the general 

 problem. 



It might be expected, then, 

 as the result of employing a 

 second regenerator coil of 

 sufficient length to produce a 

 heat interchange so complete 

 that the temperature would 

 not differ by more than one or 

 two degrees, that the gas 

 would enter the coil in the 

 liquid air chamber at a tem- 

 perature not far from — ■ 170° 

 C. instead of at — 75°, as in 

 the earlier forms of the ap- 

 paratus. The liquid air would 

 then serve to cool the gas 

 only through 15° instead of 

 through 110°, and, when the 

 apparatus was once cooled 

 down, it should consume only 

 about one fifth of the liquid 

 air required to maintain the 

 older machine in action. 



Though it is practically 

 impossible to obtain accurate 

 figures for the quantity of 

 liquid air used in an experi- 

 ment, I am satisfied that the 

 results which I had predicted 

 were fully realized in the ap- 

 paratus which I next con- 

 structed. 



The form of the liquefier 

 is shown in fig. 6. It is prac- 

 tically identical with that last 

 described, onlv the carbonic 



Fig. 6. — Hydrogen liquefier with second 

 rearenerator coil. 



acid cooling chamber is replaced by the regenerator coil Z, and con- 

 sequently the position of the escape pipe G is changed. 



