34 .PRODUCTS OF DECOMPOSITION. 



ble form. The rate at which fermentation takes place 

 in any organic substance may be said chiefly to de- 

 pend on the percentage of soluble nitrogenous matter 

 it contains ; the greater this is in amount, the more 

 quickly does fermentation go on. There are always 

 a number of soluble nitrogenous bodies in farmyard 

 manure. These are chiefly found in the urine, such as 

 urea, uric and hippuric acids, and ammonia salts. 



Products of decomposition of farmyard manure. The 

 most important of the changes which take place in the 

 rotting of farmyard manure may be briefly enumerated 

 as follows : 



1. The gradual conversion into gases of a large portion 

 of the organic elements in the manure. Of these gaseous 

 products the most abundant is carbonic acid gas (C0 2 ). 

 It is in this form that the carbonaceous matter which 

 constitutes the chief portion of the manure escapes 

 into the air. Carbon also escapes into the air, com- 

 bined with hydrogen, in the form of carluretted hydro- 

 gen or marsh-gas (CH 4 ), a product of the decomposition 

 of organic matter in the presence of a large quantity 

 of water. This gas is consequently found bubbling up 

 through stagnant water. Next to carbonic acid gas, 

 water (H 2 0) is the most abundant gaseous product of 

 decomposition. The nitrogen present in the manure, 

 in different forms, is converted by the process of 

 decomposition chiefly into ammonia, which, combining 

 with the carbonic acid, forms carbonate of ammonia, 

 a very volatile salt. It is to this fact that one of the 



