Nitrogenous organic matter passes through several intermediate compounds
during its natural decomposition, and that which does not gasify
ultimately forms nitrate. Nitrogen in organic matter is determined by
the Kjeldahl process.[13][14][58] An indication of the amount present is
obtained by the albuminoid nitrogen determination.[14][15][67][106][107]
It has not been found possible to differentiate the nitrogen in the
organic matter that readily decomposes from that in stable or
non-putrescible compounds. Decomposition of organic matter produces
nitrogen combined in ammonia, which is the first step between
nitrogenous organic matter and the completely mineralized nitrate.
Ammonia nitrogen may be determined by distillation and Nesslerization or
by direct Nesslerization of the clarified sample. The next step is
oxidation to nitrite, and the final step, oxidation to nitrate. It is
recommended that all forms of nitrogen be reported as the element
nitrogen (N).