100 ELEMENTARY AGRICULTURAL CHEMISTRY 



be preserved either by absorbents — e.g., peat-moss or dry- 

 earth — or by being collected in a tank. Access of rain should 

 be prevented by storing the manure in a covered yard. Of 

 greater complexity is the question of losses* during fermenta- 

 tion. These losses are chiefly of importance as far as they 

 affect the nitrogen. Nitrogen is lost chiefly in two ways — 

 by volatilisation of ammonia from ammonium carbonate and 

 by the evolution of free nitrogen. 



A characteristic constituent of the urine of most animals 

 is the substance known as urea, CO(NH2)2. This body is 

 by the action of micro-organisms converted into ammonium 

 carbonate : 



COCNH^)^ + 2H2O = (NHJ2CO3. 

 Urea Water Ammonium 



carbonate 



Ammonium carbonate is a substance which smells of 

 ammonia; indeed, on exposure it is said to decompose into 

 ammonia and carbon dioxide : 



(NH,)2C03 = 2NH3 + CO2 + Hp. 



Ammonium Ammonia Carbon Water 

 carbonate dioxide 



This change is hindered by the presence in the atmosphere 

 of large quantities of carbon dioxide or of ammonia. To this 

 decomposition of urea is due the strong smell of ammonia 

 generally perceptible in stables. 



In a manure heap numerous chemical changes produced 

 by micro-organisms take place, many of them attended 

 by absorption of oxygen and production of carbon dioxide. 

 Such changes evolve heat, and the temperature of the heap 

 often rises to a very high point. The oxidation of the 

 purely carbonaceous matter in the manure is rather ad- 

 vantageous, since it diminishes the quantity of useless (from 

 a manurial standpoint) matter, and thereby increases the 

 proportion of manurial matter in the residue. The high tem- 

 perature produced, however, tends to increase the amount of 

 ammonia volatilised, especially if the mass becomes dry. On 



