Two views of culture samples used to study the effect of boric acid on the production of nodules upon the roots of soy beans grown under pure culture conditions at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The samples are identified as follows (left to right): sterile, no boric acid; inoculated, no boric acid; inoculated, boric acid in the amount of 1:2,500,000; inoculated, boric acid in the amount of 1:500,000; inoculated, boric acid in the amount of 1:100,000.

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.