INFLUENCE OF AMMONIA UPON VEGETATION. 71 



and form solid carbonate of ammonia, in the form of mi- 

 nute particles appearing as a white cloud. A feather dip- 

 ped into diluted hydrochloric acid, or in vinegar, and held 

 over a bottle of ammonia water, or any substance from 

 which ammonia is escaping, is soon covered with a white 

 downy substance, which in the one case is chloride of am- 

 monia, and in the other is acetate of ammonia. This test 

 of the presence of ammonia is an easy method of distin- 

 guishing it where its escape from decomposing substances is 

 suspected. 



This gas is only little more than half the weight of air 

 (59 hundredths) ; hence it rises and is diffused in the air 

 with ease. It consists of 14 parts by weight of nitrogen 

 (82.545 per cent.) and 3 parts by weight of hydrogen 

 (17.455 per cent). 



In nature it exists in large quantity. It is almost uni- 

 versally diffused throughout the atmosphere and in the 

 surface soil and the waters of the atmosphere and the earth; 

 but it is not known to enter into any of the mineral com- 

 pounds of which the earth is composed. One exception 

 may be noted and this is guano; a substance supposed by 

 some to consist of the decomposed excrements of sea birds, 

 and by others of infusorial matter, having some relation to 

 mineral substance. But in either case guano Would be of 

 organic origin and a product of the decomposition of or- 

 ganic matter. This substance when free from earthy mat- 

 ter contains a large proportion of ammonia, both free and 

 combined, and is the most valuable and costly fertilizer 

 known. 



Ammonia chiefly exists in a state of combination as carbon- 

 ate, but also as a chloride, and a nitrate. As it combines very 

 freely with acids, and most easily with carbonic acid, it is 

 rarely found free in the atmosphere, and then only tempor- 

 arily; but it is as easily separated from its combinations, 

 on account of its volatile character which makes it readily 

 subject to the influence of heat. 



The influence of ammonia upon the growth of plants is 

 exceedingly active. It not only promotes the growth with 



