Johan Kjeldahl Introduces a New Method for Nitrogen Analysis

In 1883, Johan Kjeldahl, head of chemistry at the Carlsberg Laboratory, published a new method for determining nitrogen in organic substances. The procedure digested a sample in sulfuric acid and measured the resulting ammonia, providing a practical route to estimating the nitrogen—and, by convention, protein—content of agricultural and food materials. Kjeldahl developed the method amid the laboratory’s investigations of grain, germination, and brewing raw materials, where nitrogenous compounds affected malting and beer production. The technique was not confined to beer: its adaptability made it a long-lived standard in food, agricultural, and environmental analysis.