COS 



SirJames Dewar 



[Jan. 17, 



practical handling of liquid air, in AAhicli is shown the relation of tlie 

 boiling point to liquid composition ; while Fig. 12 shows a similar 

 relation of boiling point to the composition of the vapour : (the 

 varying density of tlie vapour is also shown). 



The respirable quality of the evaporated air will therefore vary 

 according as the liquid is^ evaporated by conduction of heat into the 

 whole quantity of li(|uid in the vacuum container, as in methods 

 2 and 3, or is" totally volatilised in successive small quantities, as in 



RELATE.D TO 



Boiling Point 



007c 

 90% 



_8PZ 

 (A) 



Oxygen Percentage in VAPOUR 



70% 



50% 

 40% 

 30% 



<A)OxYCEN Proportion and (B) Density 

 Evaporated Liquid Air 



20% 



(BL 



1A) 



Boiling Point OF Liquid 



I I \ I L 



136 



1-34 



Litre (VAPOUR 

 152 



1-30 



1-28 



1-26 



124 



1-22 



1-20 



80" 



er 



82° 



83' 



84° 



85° 



86' 



67°Abs 88" 



69" 



90" 



Fig. 12. 



the tirst (syphon) method. In the former case there will be some 

 fractionisation of the more volatile nitrogen in excess of the less 

 volatile oxygen, with the result that the vapour is less rich in oxygen 

 than the liquid ; whereas in the syphon method the liquid is succes- 

 sively evaporated as a whole, and therefore gives continuously a 



