Kjeldahl method

The Kjeldahl method is a method for determining the nitrogen content of an organic sample. It consists primarily of dissolving the organic matter in concentrated sulfuric acid resulting in the conversion of the nitrogen in the sample to ammonium sulfate, which can then be extracted from the other materials and weighed.

Process

An arbitrary nitrogen-bearing organic compound [H_*C_*O_*N_*] is dissolved in hot sulfuric acid while providing excess oxygen. This results in carbon dioxide, water, and ammonium bisulfate. The carbon dioxide escapes, and the ammonium bisulfate solution is evaporated and weighed.

See Also

Publications

• Kjeldahl, Johan Z. “A new method for the determination of nitrogen in organic bodies.” Analytical Chemistry 22 (1883): 366

Web

• A Guide to Kjeldahl Nitrogen Determination Methods and Apparatus