1903.] Amounts of Krypton and Xenon in Air. 423 



another hole in the cork there passed a siphon which could be closed 

 by means of a brass stop-cock ; this tube served to admit liquid air to 

 the balloon. A manometer was also connected with the interior of the 

 flask so as to register the pressure under which the liquid air was 

 boiling. The air boiled at a pressure of about 250 mm., corresponding 

 to a temperature of about - 195°. The boiling was quite quiet, 

 without bumping ; it was sometimes necessary to warm the balloon 

 gently in order to accelerate the evaporation. The object of distilling 

 at a low temperature was to lower the vapour-pressure of the krypton 

 and xenon in the liquid air, and so to lessen, or in great part to prevent 

 their evaporation. The total liquid air was thus reduced to about 

 200 c.c. 



The balloon containing this air was coupled with a large iron tube, 

 holding about 20 kilos, of reduced copper heated to bright redness. 

 The liquid air residue, naturally, consisted largely of oxygen, for the 

 more volatile nitrogen had in great part evaporated. After passing 

 over the copper the volume of gas was about 50 litres. 



It may be contended that during the evaporation of the air, even 

 at - 195°, a large portion of the krypton and xenon may pass away as 

 gas. It is not possible to estimate the amount lost in this manner ; 

 but at - 195°, the vapour pressure of krypton is 2*8 mm., and that of 

 xenon 0*02 mm. These figures have been arrived at in the following man- 

 ner. Eelying on the vapour pressures of mercury by Ramsay and Young, 

 given in the Trans. Chew... Soc, 1886, p. 50, and on the measurements 

 made by Ramsay and Travers* of the vapour pressures of krypton 

 and xenon, ratios were found between the absolute temperatures of 

 mercury on the one hand, and of krypton and xenon respectively on 

 the other, between the pressures 300 and 3000 mm., with two addi- 

 tional data — the temperatures of krypton corresponding to pressures 

 of 9 and of 17*4 mm. They are as follows : — 



Pressures. 



Temp, of 

 inercury. 

 Degrees 

 absolute. 



Temp, of 

 krypton. 

 Degrees 

 absolute. 



Eatios. 



Temp, of 



xenon. 

 Degrees 

 absolute. 



Eatios. 



mm. 









o 





9-0 



454°8 



94°- 2 



-1851 







300 



582 -2 



110 -4 



0-1897 



148 -9 



0-2257 



400 



596 -4 



113 8 



0-1909 



153-2 



0-2569 



500 



609 -0 



116 -1 



0-1907 



156 -8 



-2575 



600 



617-9 



118 -35 



0-1915 



159-7 



0-2583 



700 



626-5 



120-2 



0-1918 



162 -0 



-25S6 



760 



631-2 



121 -3 



0-1922 



163-9 



-2S97 



3000 



726-8 



142 -2 



0-1957 



192 -4 



0-2647 



* 'Phil. Trans.,' A, vol. 197, 1901, p. 72. 



