NITROGEN. 269 



water and oxygen gas, by simple contact, without undergoing 

 any change themselves, affording a striking illustration of 

 catalysis (page 196) ; and this decomposition may excite an 

 intense temperature, the glass tube in which the experiment is 

 made sometimes becoming red-hot. Some protoxides absorb 

 at the same time a portion of the oxygen evolved, and are 

 raised to a higher degree of oxidation, but most of them do not; 

 and certain oxides, such as the oxides of silver and gold, are 

 reduced to the metallic state, their own oxygen going off along 

 with that of the peroxide of hydrogen. The decomposition of 

 these metallic oxides cannot be ascribed to the heat evolved, 

 for oxide of silver is reduced in a very dilute solution of the 

 peroxide of hydrogen, although the decomposition is not then 

 attended with a sensible elevation of temperature. The me- 

 tallic oxides which are decomposed in this remarkable manner 

 are originally formed by the decomposition of other compounds, 

 and not by the direct union of their elements, which in fact 

 exhibit little affinity for each other. In this general character, 

 they agree with peroxide of hydrogen. 



Uses. The peroxide of hydrogen is a substance which it is 

 exceedingly desirable to possess, with the view of employing it 

 in bleaching, and for other purposes as a powerful oxidating 

 agent. But the expense and uncertainty of the process for pre- 

 paring this compound have hitherto prevented any application 

 of it in the arts, or even its occasional use as a chemical re- 

 agent. 



SECTION III. 

 NITROGEN. 



Synonyme, AZOTE. Equiv. 177, or 14.2 on hydrogen scale ; 

 symbol N ; density 976 ; combining measure \ | [. 



Dr. Rutherford of Edinburgh examined the air which re- 

 mains after the respiration of an animal, and found that after 

 being washed with lime-water, which removes carbonic acid, 

 it was incapable of supporting either combustion or respiration. 

 He concluded that it was a peculiar gas. Lavoisier afterwards 

 discovered that this gas exists in the air of the atmosphere, 

 forming indeed 4-5ths of that mixture, and gave it the name 

 azote, (from , privative, and w>/, life), from its inability to 



