THE CULTURE OF FARM CROPS. 



CHAPTER V. 



HYDROGEN AND NITROGEN AND THEIR COMPOUNDS. 

 THEIR RELATION TO VEGETABLE GROWTH. 



Hydrogen, like oxygen, is a colorless, tasteless gas with- 

 out any odor; slightly soluble in water and exceedingly 

 inflammable. It is never found free, but always in combin- 

 ation, forming one-ninth by weight of water, and a consid- 

 erable proportion of all organized matter. When combined 

 with nitrogen in the proportion of three parts to one of the 

 latter it forms ammonia, and this compound is always 

 formed during the decomposition of organic matter. Its 

 part in the formation of water by the union of one part with 

 eight parts of oxygen gives to it, its greatest importance in 

 the economy of nature ; and its name hydro-gen or "gener- 

 ator of water" is derived from this, its chief property. 

 But it is no more entitled to this name than oxygen is, but 

 received it because it was discovered and became known a 

 few years before oxygen. The English chemist, Cavendish, 

 first discovered it as an element in 1766. The only impor- 

 tant solid mineral into whose composition it enters is coal. 



This gas is the lightest of all known substances being 14 J 

 times lighter than air, and hence is employed to inflate 

 balloons. It will not support life, but is not noxious ; an 

 animal immersed in it dies simply for want of oxygen. 

 When mixed with oxygen and ignited, the gases explode 

 violently and water is formed. It burns when pure with a 

 light blue flame, giving out intense heat, but very little 

 light and also forms water. When mixed with carbon, it 

 forms the common marsh gas, and the fatal fire-damp of 

 coal mines. This gas is produced by the decomposition of 

 vegetable matter and accompanies the fermentation of man- 

 ure in heaps in the barn yard. When mixed with air it is 



