1919] 



on Liquid Oxygen in Warfare 



601 



OXYGEX SUPPLY IN UPPER AIR. 

 EVAPORATIOX AT REDUCED PRESSURES. 



When respirators are employed in aerial navigation they are 

 subjected to changing conditions of temperature and pressure 

 with varying altitude. When ascending the lowering of external 

 pressure (Fig. 6) causes a considerable increase in the normal rate 

 of evaporation of the liquid oxygen in the container. This is 



B 



AROMETER with ALTITUDE 



10 



20 



Amount 



30 CM'^ Hg 40 



: Lowering 



Fig. 6. 



50 60 



Barometer 



70 



shown by the curve (Fig. 7) comparing the normal loss with 

 the additional evaporation caused by lowering of external pressure. 

 When descending the process is reversed, so that not only evaporation 

 may cease, but recondensation may take place should the release 

 valve leak at all. The temperature alterations which occur at the 



