General view of an apparatus used to facilitate the adsorption of silica gel and nitrogen oxide at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Adsorption refers to a surface phenomenon in which particles or molecules bind to the top layer of a material. It is distinguished from the process of absorption, in which a substance diffuses into a liquid or solid to form a solution.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American University in 1919 under the directorship of Arthur B. Lamb. Initially part of the War Department, the F.N.R.L. was the successor to several wartime initiatives to develop a secure domestic supply of nitrate compounds necessary for the manufacture of explosives during World War I. With a staff of about 110 individuals, including 35 to 50 chemists, the F.N.R.L. focused on the manufacture, production, and development of products of atmospheric nitrogen, including munitions and fertilizers.