General Principles. 47 



of the present day (Sir Humphry Davy) has 

 given the name of the nitrous oiide. It may 

 be taken into the lungs by breathing, to a certain 

 degree, with no dangerous consequences. But 

 the effect is a momentary intoxication with ex- 

 ceedingly pleasurable sensations. The effects, 

 however, cease in a very little time, and leave no 

 sensation of languor behind, as in other cases of 

 intoxication. The proportion of the ingredients 

 is supposed to be about seven parts of oxygen to 

 thirteen of nitrogen. 



The other is that which is called nitrous gas, 

 and which is merely an unsaturated combination 

 of nitrogen with oxygen. Hence it has a very 

 strong attraction for oxygen, which it takes even 

 from the atmospheric air. When brought into 

 contact with common air, therefore, it rapidly 

 absorbs the oxygen from it, forming nitric acid, 

 and consequently destroys a certain portion of 

 the mass. Hence it was employed as a test 

 of the purity of air (more properly of the quan- 

 tity of oxygen it contained), and an instrument 

 was constructed called the eudiometer. This 

 was only a glass tube, such as that exhibited in 

 the pneumatic apparatus, fig. 19. In this was 

 included a certain portion of any air which was 

 meant to be tried ; to this nitrous gas was ad- 

 mitted ; and in proportion as the air in the tube 

 was lessened (that is, in proportion to the dimi- 

 nution of the oxygen), the air was supposed to 

 be more or less pure. Nitrous gas is estimated, 



