Kjeldahl flask

Description (Brief)
This object is a 300 mL Kjeldahl flask made by the Rheinische Glashutten-Actien-Gesellschaft.
In 1883 Danish chemist Johan Kjeldahl (1849–1900) of the Carlsberg Laboratory published the Kjeldahl method. It was the first accurate, simple, and speedy way to determine nitrogen content in organic matter.
Kjeldahl’s employer, Carlsberg Laboratory, had been originally established as a place for scientific research to perfect the process of beer making. Later, the laboratory took on a broader mission to contribute to pure research. The need for the Kjeldahl method grew from his analysis of the protein content of grains for beers at different stages—from germination to fermentation as beer wort. Analyses of nitrogen content can be used to quantify the amount of protein in a sample, and protein content of grains influences the volume of beer they produce.
The Kjeldahl method proved to have wide-ranging applications and was quickly adopted by scientists from a variety of fields. In the mid-2010s, the method (with minor modifications) was still in use for purposes ranging from analysis of protein in foods to nitrogen content in soil samples. To “Kjeldahl” a sample has become a verb in chemical parlance, considered by some the greatest honor bestowed by the chemical community.
Along with his method, Kjeldahl’s name also became attached to a piece of laboratory equipment he developed in 1888. The long-necked, round-bottomed flask was ideal for avoiding splashback when heating solutions. Splashback was a threat during the first step of the Kjeldahl method—which requires heating the sample in concentrated sulfuric acid.
Rheinische Glashutten-Actien-Gesellschaft was a German glassworks located in Ehrenfeld, Cologne, from 1872 through 1937. The company introduced a chemically resistant glass, similar to Jena glass, for laboratory use as early as 1909.
This object is part of a collection donated by Barbara Keppel, wife of C. Robert Keppel. Robert Keppel taught at the University of Nebraska-Omaha after receiving his B.S. in Chemistry from the University of California, Berkeley, and his Ph.D. in organic chemistry from M.I.T. The glassware in the Keppel collection covers the 19th and early 20th centuries.
Burns, D. Thorburn, and W. I. Stephen. “Kjeldahl Centenary Meeting.” Analytical Proceedings 21, no. 6 (1984): 210–20. doi:10.1039/AP9842100210.
Buse, Stephan. “Eine Wieder Entdeckte Preisliste Der Rheinischen Glashütten AG Ehrenfeld Bei Köln von 1877 - Hartglas Nach Dem Verfahren A. de La Bastie.” Pressglas-Korrespondenz 4, September (2007).
Cauwood, J.D., and W.E.S. Turner. “The Attack of Chemical Reagents on Glass Surfaces, and a Comparison of Different Types of Chemical Glassware.” Journal of the Society of Glass Technology 1 (1917): 153–62.
National Museum of American History Accession File #1985.0311
Sáez-Plaza, Purificación, Tadeusz Michałowski, María José Navas, Agustín García Asuero, and Sławomir Wybraniec. “An Overview of the Kjeldahl Method of Nitrogen Determination. Part I. Early History, Chemistry of the Procedure, and Titrimetric Finish.” Critical Reviews in Analytical Chemistry 43, no. 4 (2013): 178–223. doi:10.1080/10408347.2012.751786.
Sella, Andrea. 2008. “Classic Kit: Kjeldahl Flask.” Chemistry World. http://www.rsc.org/chemistryworld/Issues/2008/May/KjeldahlFlask.asp.
“University of Nebraska Omaha.” 2015. Accessed May 4. http://www.unomaha.edu/college-of-arts-and-sciences/chemistry/student-opportunities/scholarships.php.
Currently not on view
Object Name
flask, kjeldahl
date made
Rheinische Glashutten-Actien-Gesellschaft
Physical Description
glass (overall material)
overall: 23.2 cm x 7 cm; 9 1/8 in x 2 3/4 in
ID Number
catalog number
accession number
Science & Scientific Instruments
See more items in
Medicine and Science: Chemistry
Science & Mathematics
Science Under Glass
Data Source
National Museum of American History, Kenneth E. Behring Center


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