Johan Kjeldahl
| Johan Kjeldahl | |
|---|---|
Danish chemist
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| Born |
16 August 1849 Copenhagen, Denmark |
| Died | 18 July 1900 (aged 50) Tisvildeleje, Denmark |
Johan Gustav Christoffer Thorsager Kjeldahl (Danish pronunciation: [johan ˈkʰɛld̥æːˀl] 16 August 1849 – 18 July 1900), was a Danish chemist who developed a method for determining the amount of nitrogen in certain organic compounds using a laboratory technique which was named the Kjeldahl method after him.
Kjeldahl worked in Copenhagen at the Carlsberg Laboratory, associated with Carlsberg Brewery, where he was head of the Chemistry department from 1876 to 1900.
He was given the job to determine the amount of protein in the grain used in the malt industry. Less protein meant more beer. Kjeldahl found the answer was in developing a technique to determine nitrogen with accuracy but existing methods in analytical chemistry related to proteins and biochemistry at the time were far from accurate.
In order to solve the problem of determining accurate nitrogen content in a sample, Kjeldahl developed a method which involves a two-step reaction: a distillation and a back titration. He found that ammonium salts can be produced by the reaction between organic compounds and sulfuric acid; this step is a digestion. Ammonium salts produced from this step were collected and, in a second process, reacted with lye. The ammonia produced in this step was distilled and dissolved in a standardized solution of hydrochloric acid or sulfuric acid. Finally, this solution was back titrated with caustic soda to indirectly measure nitrogen.
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