CHAPTER V 
NITRIFICATION AND DENITRIFICATION 
NITRIFICATION 
The pulling of the organic nitrogen compounds to pieces does 
not in itself bring the nitrogen into the best available condition for 
plants. It is in the form of nitrates that plants most readily 
absorb nitrogen, and at the end of the decompositions noticed 
ammonia compounds are formed, but no nitrates. Some plants 
are able to absorb nitrogen in the form of ammonia salts, but by 
far the largest amount is assimilated in the form of nitrates. 
Consequently, if these decomposition products are to be utilized 
by plants, they need to be changed from ammonia salts into 
nitrates. This process has been called nitrification. 
Nitrification is a process of oxidation. In the oxidation of am- 
monia compounds to form nitrates there are two separate stages. 
The first is one by which the ammonia is oxidized into a ntirite. 
A nitrite is a salt of nitrous acid (HNOz), and it contains less oxy- 
gen than a nitrate. Nitrites are not plant foods, for, as far as 
known, ordinary plants never absorb nitrogen in this form. The 
second change is the addition of another atom of nitrogen to the 
nitrite, giving a nitrate or salt of nitric acid (HNOs3), the form in 
which the nitrogen is most completely available for plants. 
Nitrates are really of very great significance in nature. They 
are readily soluble in water, so that they are easily taken up by the 
soil and absorbed by the roots; thus nitrates feed the whole world 
of green plants. In addition to this, nitrates form the basis of 
most explosives. Gunpowder has saltpeter as its basis, and salt- 
peter is nitrate of potash. Nitroglycerin, too, is made from nitric 
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