1911>] 



on Liquid Oxygen in Warfare 



59' 



In many forms the cap C was made into a vacnam jacket stopper, 

 provided as usual with a little charcoal for making* the vacuum more 

 effective when the cap became cooled. The object of the vacuum 

 stopper is to guard against too rapid a flux of heat, and consequent 

 rise of pressure by splashing or inclination of the contained oxygen 

 in the glass vacuum vessel. 



The vessels are liable to excessive loss \)j too rapid evaporation 

 through the blow-off valve. This is likely to occur when the bore of 

 the outflow syphon tube is too small. The liquid is not freely delivered 

 into the evaporator, where there is ample space and surface for smooth 

 boiling, but is partly volatilised in the narrow outlet tube. Con- 

 sequently back surges of pressure into the container occnr with 



Fig. 4. 



accompanying rashes of evaporated oxygen, lost through the valve. 

 This is most marked when the vessel is full and the free space 

 therefore small. AVhen a vacuum syphon delivery tube was fitted 

 this did not occur. 



With the evaporating chamber in the form of a spiral of copper 

 tube (equivalent to restrictino- the free space without reducing the 

 heating surface), the irregularities on continuous working were greatly 

 increased, and the loss through the blow-off sometimes actually ex- 

 ceeded the rate of delivery. With a larger metal apparatus consist- 

 ing of a 8-litre nickel vacuum container whose evaporator was in 

 the form of three cylindrical brass vessels (capacity 200 cubic centi- 

 metres each), connected by coils of |-inch copper tubing, the loss 



