798 Mr. F. B. Young on the 



J3 



raise the pressure by gently heating the upper part of the 

 tube. 



Since the removal of gaseous impurity was of the utmost 

 importance, the methods of filling were carefully examined. 

 Tube XII. was filled with excess of ether and connected 

 through a prolongation of the capillary D (fig. 2) and a 

 short piece of rubber pressure-tubing to a Topler pump. 

 The ether having been frozen with liquid air, the tube was 

 exhausted. When the ether was allowed to thaw a brisk 

 effervescence of bubbles proceeded from the surface of the 

 dwindling solid lump. This was the dissolved air which had 

 separated out when the ether was frozen. Not all the air, 

 however, escaped in this way. After a little of the ether 

 had vaporized, the freezing and thawing were repeated and 

 again bubbles were evolved, though fewer than before. 

 Though the ether was frozen four times, a few bubbles rose 

 after the final thawing. (In the case of another tube bubbles 

 were evolved after the ninth freezing.) The trouble was 

 largely due to the partial solution of the bubbles as they 

 rose, for some of the smaller bubbles visibly dwindled in 

 size as they ascended. The tube was finally sealed off at the 

 constriction whilst the ether vapour was passing freely into 

 the pump. 



For purposes of comparison another tube A was filled with 

 ether. The constricted end had been drawn out and bent so 

 that the tip might be immersed in mercury. About two- 

 thirds of the ether was boiled off and the tube was then 

 sealed. Tubes XII. and A were then immersed in liquid 

 air : when the ether thawed, an eye estimation of the bubbles 

 evolved led to the conclusion that tube A contained rather 

 more permanent gas than tube XII. 



The importance of reducing the pressure to a minimum, 

 if the freezing process is employed, was shown by freezing 

 and thawing ether at atmospheric pressure. Though 

 numerous bubbles appeared upon the surface of the solid lump 

 as it melted away, scarcely one left the surface, so rapidly 

 did they dissolve. 



A further test showed the extreme solubility of air in 

 ether at the atmospheric pressure. A tube which had been 

 nearly freed from permanent gas in the manner above 

 explained was detached from the pump, so that the ether 

 was again exposed to the atmosphere. After a few moments 

 it was replaced on the pump, care being taken to avoid 

 shaking the tube more than was necessary. On freezing 

 the ether and thawing it under reduced pressure, the effer- 

 vescence was not perceptibly less than it had been originally. 



These tests suggest that the test commonly relied upon for 



