Oxide, Carbonic Anhydride, and Nitrous Oxide. 207 



nitrogen. In the case of the commercial supply, a better result is 

 obtained by placing the bottles in an inverted position so as to draw 

 from the liquid rather than from the gaseous portion. 



Higher and more consistent results were arrived at from gas which 

 had been specially treated. In consequence of the high relative 

 solubility of nitrous oxide in water, the gas held in solution after 

 prolonged agitation of the liquid with impure gas from any supply, 

 will contain a much diminished proportion of nitrogen. To carry 

 out this method on the scale required, a large (11-litre) flask was 

 mounted on an apparatus in connection with the lathe so that it 

 could be vigorously shaken. After the dissolved air had been suffi- 

 ciently expelled by preliminary passage of N 2 0, the water was cooled 

 to near 0° C. and violently shaken for a considerable time while the 

 gas was passing in large excess. The nitrous oxide thus purified was 

 expelled from solution by heat, and was used to fill the globe in the 

 usual manner. 



For comparison with the results so obtained, gas purified in another 

 manner was also examined. A small iron bottle, fully charged with 

 the commercial material, was cooled in salt and ice and allowed 

 somewhat suddenly" to blow off half its contents. The residue drawn 

 from the bottle in one or other position was employed for the 

 weighings. 



Nitrous Oxide (1896). 



Aug. 15 Expelled from water 3*6359 



„ 17 , 3-6354 



„ 19 From residue after blow off, valve downwards 3*6364 



,, 21 „ ,, valve upwards . . 3*6358 



„ 22 „ „ valve downwards 3*6360 



Mean 3*6359 



The mean value may be taken to represent the corrected weight of 

 the gas which fills the globe at 0° C. and at the pressure of the gauge 

 (at 15°), corresponding to 2*6276 for oxygen. 



One of the objects which I had in view in determining the density 

 of nitrous oxide was to obtain, if it were possible, evidence as to the 

 atomic weight of nitrogen. It may be remembered that observations 

 upon the density of pure nitrogen, as distinguished from the atmo- 

 spheric mixture containing argon which, until recently, had been 

 confounded with pure nitrogen, led* to the conclusion that the densi- 

 ties of oxygen and nitrogen were as 16 : 14*003, thus suggesting that 

 the atomic weight of nitrogen might really be 14 in place of 14*05, 

 as generally received. The chemical evidence upon which the latter 

 number rests is very indirect, and it appeared that a direct compari- 



* Eayleigh and Kamsay, ' Phil. Trans.,' vol. 186, p. 190, 1895. 



