x NITRE, NITRIC ACID, AND NITROGEN 193 



Composition of nitrous oxide. The first successful 

 analysis was carried out by Davy (circ. 1800) in the case of 

 the diminished nitrous air or " laughing gas," to which he 

 gave the name NITROUS OXIDE. The gas was analysed by 

 burning charcoal in it : the proportion of oxygen was 

 calculated from the volume of carbonic anhydride produced, 

 whilst the nitrogen left after the combustion was measured 

 directly. The gas, generated from nitrate of ammonia, 

 " was in its highest state of purity, as it left a residuum of 

 ^- only, when absorbed by boiled water." 



" Ten cubic inches of it were inserted into a jar graduated 

 to OT cubic inch, containing dry mercury. Through this 

 mercury a piece of charcoal which had been deprived of its 

 hydrogen by long exposure to heat, weighing about a grain, 

 was introduced, while yet warm. No perceptible absorption 

 of the gas took place." 



" Thermometer being 46, the focus of a lens was thrown 

 on the charcoal, which instantly took fire, and burnt vividly 

 for about a minute, the gas being increased in volume. 

 After the vivid combustion had ceased, the focus was 

 again thrown on the charcoal ; it continued to burn for 

 near ten minutes, when the process stopped." 



" The gas, when the original pressure and temperature 

 were restored, filled a space equal to 12*5 cubic inches" 

 (Davy's Works, III. 59-60). 



An examination of the residue showed that 5*2 cubic inches 

 of the gas had been decomposed, giving rise to 2*4 cubic inches 

 of carbonic anhydride (condensed by the addition of 

 ammonia) and 5*1 cubic inches of nitrogen, whilst the other 

 4'8 cubic inches were unchanged and could be dissolved out 

 by means of boiled water. Knowing the proportion of 

 oxygen in the carbonic anhydride, and the densities of 

 nitrogen and of nitrous oxide, Davy was able to conclude : 



" that 100 grains of nitrous oxide are composed of 37 

 oxygen and 63 nitrogen : existing in a much more con 

 densed form than when in their simple forms." 



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