1920-21.] Evaporation of Liquid Air in Vacuum Flasks. 97 
ft 
X. — An Experimental Analysis of the Losses by Evaporation 
of Liquid Air contained in Vacuum Flasks. By Professor 
Henry Briggs, D.Sc. 
(MS. received March. 1, 1921. Read March 21, 1921.) 
The experiments here described were made on behalf of the Oxygen 
Research Committee of the Scientific and Industrial Research Department, 
and the paper is given by permission of the Department. The fullest 
acknowledgment is due to Dr J. A. Harker, F.R.S., and to his co-workers, 
Professor G. W. Todd and Mr S. H. Groom, who have, in a series of able 
memoirs presented to the Oxygen Committee, analysed the nature of the 
heat-transfer from the outer atmosphere to the interior of metal vacuum 
bottles; but for their memoirs the writer’s experiments would not have 
suggested themselves. 
The Dewar Vacuum Vessel. 
The Dewar vacuum flask, which enables low boiling-point liquids to 
be stored and transported, has been the principal means of rendering 
possible the great expansion now proceeding in the scientific and com- 
mercial uses of liquid air and liquid oxygen. These liquids are being 
increasingly employed as laboratory reagents, and are being put to service 
in mine rescue apparatus, for blasting, in aviation and therapeutics, and 
in evacuation plant. 
Vacuum vessels are made in glass, silica ware, porcelain, and metal; 
but for carrying and handling the liquids in bulk, only the last kind is 
at present of much value. The glass vessels devised by Dewar in the 
course of his researches on liquefied gases, and made by him in many forms, 
are too well known to need description.* 
Dewar described the metallic vacuum vessel in 1906, f and not long 
after that date its manufacture was taken up in Germany, whence, before 
the war, all the flasks required at British mine rescue stations were 
obtained. During the latter part of the war these bottles became necessary 
for the Services, and as a result of the exertions of makers and of the 
* Sir James Dewar, “Liquid Atmospheric Air,” Proc. Roy. Inst . , xiv (1893), p. 1; 
“The Coming of Age of the Vacuum Flask,” ibid., xxi, p. 240. 
t Ibid., “ Studies on Charcoal and Liquid Air,” xviii, p. 439. 
VOL. XLI. 
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