Critical Phenomena of Ether. 801 



ether in the experimental tubes and the remainder in G. 

 The ether was distilled to and fro between F and (x, the 

 operations above described being repeated at each reversal. 

 In this way the first and last fractions were each time 

 removed, and the experimental tubes were flushed out with 

 ether vapour. K was so manipulated as to prevent the 

 return of any vapour from the pump. The distillation was 

 accelerated, when necessary, by dipping the reservoir in a 

 beaker of methylated spirit, and the spirit served the further 

 useful purpose of keeping the reservoir free from frost, so 

 that careful observation was possible. The bubbles evolved 

 on thawing decreased at each successive distillation till at 

 the commencement of the sixth distillation none were visible. 

 The sixth distillate was then frozen and allowed to thaw, 

 whilst one of the empty tubes was immersed in liquid air in 

 order that the ether might thaw under a minimum pressure. 

 As there was again an entire absence of bubbles, the process 

 of the purification was considered complete. Each experi- 

 mental tube in turn was then filled by condensation with a 

 slight excess of ether ; the excess was distilled off, and the 

 tube sealed off at the constriction with the blow T pipe. 



Some of the tubes were sealed whilst the vapour was 

 issuing freely ; others were immersed, before sealing, in 

 liquid air, so that the constriction was free from vapour. 

 The latter tubes showed a slight but distinct superiority over 

 the former when tested for the presence of permanent gas. 

 From this it appears that the vapour in contact with the hot 

 glass undergoes decomposition. 



For the above process, Kahlbaunr's ether distilled over 

 sodium was used after further treatment. About a third of 

 a litre of the ether was placed in a well-stoppered bottle with 

 some sodium and potassium alloy. The bottle was wrapped 

 in opaque paper and placed in a mechanical shaker, by means 

 of which it was repeatedly shaken for several hours at a 

 time. This plan was adopted in view of a suggestion that 

 the efficiency of the solid metal is quickly impaired by the 

 oxidation of the surface : by means of the shaking the surface 

 of the liquid alloy was constantly renewed. After about 

 three months of this treatment the ether was fractionated 

 over the alloy three times through a five-section Young 

 fractionating column. The ether was protected from atmo- 

 spheric moisture by a guard-tube of phosphorus pentoxide, 

 the receiver ^being ground to the condenser tube ; and by 

 introducing the liquid into the apparatus in the manner 

 previously described, the necessity for pouring it through 

 the air was avoided. The thermometer employed was 



