Front lateral view of an infrared spectrograph used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Visible components of the spectrograph include the thermocouple vacuum system and the moving plate holder. An individual identified as Mr. Liddel is seen adjusting the vernier setting of the Littrow mirror.

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.