Kjeldahl digestion and distillation apparatus, accession no.46; 1938
In the late 19th century, Danish chemist Johann Kjeldahl devised a method of the determination of nitrogen. Protein was digested by sulfuric acid and catalyst over gas flames, with vapor vented. Nitrogen, trapped in the form of ammonium sulfate, was subsequently released as free ammonia and titrated. By the time Dr. Donald D. Van Slyke used this version of the Kjeldahl apparatus, it had been standardized and was sold commercially.
Photo by Lubosh Stepanek
Johann Kjeldahl, Donald D. Van Slyke, Kjeldahl apparatus