Discuter:Johan Kjeldahl

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Carlsberg Laboratory today, in the front statue of Johan Kjedahl.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 develop an accurate technique that may determine nitrogen with accuracy but methods on analytical chemistry related to proteins and biochemistry at the time were far from accurate thus swedish chemist Jons Berzelius and his colleagues in western europe during the late 19th century were on the eve of biochemistry research.

[edit] Kjeldahl method Main article: Kjeldahl method

In order to solve the problem of determining nitrogen content in a sample, Kjeldahl developed a method which involves a two-step reaction: a distillation process and finally back titration. He found ammonia salts can be produced by the reaction between organic compounds and sulfuric acid; this step he called digestion. Ammonia 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 standarized solution of Hydrochloric acid or sulfuric acid. Finally, this solution was back titrated with caustic soda to measure nitrogen.

During the 1880s Kjeldahl used potassium sulfate to raise the boiling point of the acid and mercury as a catalyst to speed the decomposition. For the back titration process of the released ammonia he used boric acid buffer solution.

On March 7, 1883, Kjeldahl presented his method at the Danish Chemical Society.

Johan Kjeldahl on the 1880s working at Carlsberg Laboratory.[edit] Final days and legacy Johan Kjeldahl died on July 18, 1900 in Copenhagen, Denmark at the age of 53.

His laboratory technique for Nitrogen and protein analysis at the Carlsberg brewery is still the universally accepted method for this analysis. Although other methods claim to be faster and more efficient, none can cope with the variety of sizes or conditions of samples than Johan Kjeldahl's original method. Kjeldahl equipment is used extensively all over the world.

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