THE VOLATILE PAKT OF PLANTS. 23 



incapable of supporting combustion is proved by the first 

 method, we have instanced for its preparation. 



Exp. 10.— A burning splinter la Immersed In the bottle containing the 

 nitrogen prepared by the second method, Exp. 9; the flame immediate- 

 ly goes out. 



Nitrogen cannot maintain respiration, so that animals 

 perish if confined in it. Vegetation also dies in an at- 

 mosphere of this gas. For this reason it was formerly 

 called .Azote (against life). In general it is difficult to 

 effect direct union of nitrogen with other bodies, but at 

 a high temperature, in presence of alkalies, it unites with 

 carbon, forming cyanides. 



The atmosphere is the great store and source of nitro- 

 gen in nature. In the mineral kingdom, especially in 

 soils, it occurs in small relative proportion, but in large 

 aggregate quantity as an ingredient of saltpeter and other 

 nitrates, and of ammonia. It is a constant constituent 

 of all plants, and in the animal it is a never-absent com- 

 ponent of the working tissues, the muscles, tendons and 

 nerves, and is hence an indispensable ingredient of food. 



Hydrogen. — Water, which is so abundant in nature, 

 and so essential to organic esSstence, is a compound of 

 two elements, viz. : oxygen, that has already been consid- 

 ered, and hydrogen, which we now come to notice. 



Hydrogen, like oxygen, is a gas, destitute, when pure, 

 of either, odor, taste, or color. It does. not occur nat- 

 urally in the free state, except in small quantity in the 

 emanations from boiling springs and volcanoes. Its most 

 simple preparation consists in abstracting oxygen from 

 water by means of agents which have no special affinity 

 for hydrogen, and therefore leave it uncombined. 



Sodium, a metal familiar to the chemist, has such an 

 attraction for oxygen that it decomposes water with great 

 rapidity. 



Exp. 11.— Hydrogen is therefore readily procured by Inverting a bot- 

 tle full of water in a bowl, and inserting into it a bit of sodium as large 

 as a pea. The sodium should first be wiped tree from the naphtha in 



