Nitrogen‐Total

The determination of total nitrogen (N) in soils and other complex heterogeneous materials containing several forms of N presents many difficulties. A.W. J., Dyck and R. R. McKibbin analyzed 26 organic soils by Dumas and Kjeldahl methods and found that with every sample tested, the Dumas method gave a considerably higher N value. The Kjeldahl procedures generally employed for determination of total N involves two steps: digestion of the sample to convert organic N to NH4 -N and determination of NH4-N in the digest. The acid consumption value for the organic fraction of soils is much higher than the corresponding values for the inorganic soil constituents, and acid consumption during Kjeldahl digestion of organic soils can exceed 6 mUg of soil. Although several methods have been proposed for direct determination of NH4 in Kjeldahl digests, this determination is usually performed by estimation of the NH3 liberated by distillation of the digest with strong alkali.

Перевод пока недоступен