General view of apparatus use to determine total and partial vapor pressures at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The apparatus was commonly used to measure the total vapor pressure of vapor emitted from the reaction of liquid carbon dioxide and liquid ammonia, as well as the partial pressures of carbon dioxide, ammonia, and water.

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.