48 Fertilizers 



uct of the decay of a nitrogenous organic substance 

 is ammonia, a combination of two elements, hydrogen 

 and nitrogen. As the organic animal or vegetable sub- 

 stance which contains carbon, hydrogen, oxygen and 

 nitrogen in combination breaks up, the carbon combines 

 with part of the oxygen to form carbonic acid; part of 

 the hydrogen also combines with oxygen to form water, 

 and the nitrogen combines with hydrogen to form am- 

 monia. Yet even in this form, plants do not absorb it 

 freely. Ammonia is in a better form than the organic 

 material, because, in the first place, it is soluble in most 

 of its combinations with other substances, and is thus 

 readily distributed in the soil, and in the second place, 

 it is very liable to change. That is, its future availability 

 is no longer dependent upon any mechanical or physical 

 form; every portion or pound of ammonia is as good as 

 any other portion or pound. Ammonia, however, does 

 not occur as a natural product, like the organic forms, 

 blood, meat and fish. Commercial forms are the result 

 of a manufacturing process, and they may exist as dis- 

 tinct chemical substances; as sulfate of ammonia, in 

 which case the ammonia is combined with sulfuric acid; 

 as chlorid of ammonia, in which case it is combined with 

 hydrochloric acid; as nitrate of ammonia, in which case 

 it is combined with nitric acid ; and as carbonate of am- 

 monia, in which case it is combined with carbonic acid. 

 Sulfate of ammonia is a chemical salt which, when pure, 

 contains 21.2 per cent of nitrogen. In commercial 

 forms, however, it usually contains about 20 per cent 

 of nitrogen. It is obtained from the dry distillation of 

 animal bone in the manufacture of bone-black, from the 

 distillation of coal in the manufacture of illuminating 

 gas, and from coal in the manufacture of coke. The 



