Kjeldahl determination

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Kjeldahl determination Widely used method of determining total nitrogen in a substance by digesting with sulphuric acid and a catalyst; the nitrogen is reduced to ammonia which is then measured. In foodstuffs most of the nitrogen is protein, and the term crude protein is the total ‘Kjeldahl nitrogen’ multiplied by a factor of 6.25 (since most proteins contain 16% nitrogen). Invented in 1883 by Johan Gustav Christoffer Thorsager Kjeldahl (1849–1900), Danish chemist.