ATTAINMENT OF VERY LOW TEMPERATURES. 



19 



to escape and return to the gasometer in case the expansion valve E 

 becomes blocked. After 

 passing through A, the 

 compressed gas passes 

 through the coils in the 

 chambers B and C. The 

 chamber B contains 

 liquid air, some of which 

 is allowed to flow into C 

 through a pin valve 

 which is regulated by 

 the rod h. The liquid 

 air in C evaporates un- 

 der a pressure of about 

 100 millimeters of mer- 

 cury, an exhaust being 

 maintained by means of 

 a pump communicating 

 with B through the tube 

 /, and reduces the tem- 

 perature of the com- 

 pressed gas to below 

 — 200° C. The total 

 length of coil in the 

 chamber C is about five 

 meters. The gas then 

 enters the regenerator 

 coil D, 180 mm. long 

 and 50 mm. diameter, 

 and passing through it 

 expands at the valve E, 

 which is controlled by 

 means of the valve-rod 

 and lever a. The ex- 

 panded gas passes up- 

 wards through the in- 

 terstices of the regenera- 

 tor coil, and returns by 

 way of the annular space 

 F and the tube G to the 

 compressor. 



The accompanying Fig. 4.— Section of hydrogen liquefier. 



diagram of this appar- 

 atus shows clearly how the gas-tight connection between the outer vvaK 



