602 



Sir James Dewar 



[Jan. 1' 



same time counteract in some measure; the effects caused \)j altering 

 pressure. The response of the evaporators to such conditions was 

 examined by the arrangement shown in Fig. 8. The dehvery valve 

 y of a container A fitted for electrical evaporation was connected to 

 a small vacuum pump B capable of maintaining a pressure of a few 

 millimetres of mercury with a very rapid evaporation. The delivery 

 was measured on a gas meter (not shown) connected to the pump 

 outlet. The lowering of pressure was measured on a mercury 

 barometer column C between the pump and the evaporator. A 



looL 



Cramsl 

 Evoporated 

 90l_ 



80 



60 



50_ 



30 



20 



Loss OF Liquid Oxygen at Low Pressure 



(AH atmosphere Lteady external Pressure 

 (B) -^ atmosphere) 



2 Kilos; in container with release vaive 

 opening at + 0-25atm 



\oss 



(^ 



20 



Fig. 



10-12 litre flask D was included in the circuit as an equaliser, while 

 the three-way stop cock E served to regulate and stabilise the pressure 

 as required. The rate of delivery at successive reductions of the 

 heights of the barometer was thereby quickly measured, as well as 

 the response of the machine to rapid alterations of height, up and 

 down. A manometer was connected to the container to show the 

 pressure at which the liquid was boiling. The indications of both 

 manometer and barometer are shown in the curves (Fig. 9). Before 

 applying the exhaust, the blow-off pressure at the release valve was 

 steady at 18 centimetres of mercury al)ove the atmospliere. 



