General view of Dr. E.W. Guernsey demonstrating an apparatus used to study the formation of nitric oxide in the explosion of carbon monoxide and oxygen at the U.S. Department of Agriculture's Fixed Nitrogen Research…

Two views of Dr. F.E. Allison studying the fixation of nitrogen by bacteria at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory…

General view of Dr. J.G. Thompson (left) and Mr. C.L. Sullivan (right) operating a hydrogen burner during the production of the hydrogen-nitrogen mixture used in the synthesis of ammonia at the U.S. Department of…

General view of Dr. J.G. Thompson demonstrating use of an ammonia catalyst fusion pot at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research…

General view of Dr. M.F. Fogler demonstrating an apparatus used for the dissociation of nitric acid at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed…

General view of Dr. R.O.E. Davis demonstrating use of an apparatus for filling tubes in order to study ammonia-carbon dioxide-Urea-water systems at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

General view of Dr. Sebastian Karrer using an apparatus to measure the thermal conductivity of active nitrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The…

General view of Mr. E.H. Johnston demonstrating an apparatus used for the production of ozone at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

General view of E.J. Fox and K.S. Love at work in the Nitrogen Analytical Laboratory at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory facilities located in Washington, D.C. Assorted glassware…

General view of E.J. Fox demonstrating use of a rotary tunnel to facilitate the absorption of nitric oxides by ground phosphate rock at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

General view of E.J. Fox demonstrating use of towers to facilitate the absorption of nitric oxides by phosphate rock at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.…

Electric arc furnace used to make ferro-aluminum alloys at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American…

General view of electrolytic cells used for the production of hydrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory…

General view of the electron inertia apparatus used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was…

General view of the electrical shop at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory showing assorted machinery and apparatus. The man visible on the left-hand side of the photograph is…

Equipment used to treat raw materials for the production of fertilizer with nitrogen oxides at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

Exhibition display concerning the fixation of atmospheric nitrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The display includes several diagrams depicting…

General view of an experimental apparatus to test the production of hydrogen from methane and steam at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed…

Assorted views of slag being tapped from the experimental blast furnace at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The individuals visible in the photographs…

General view of an experimental furnace used to smelt phosphate rock at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory…

General view of the exterior of the Fixed Nitrogen Research Laboratory's Urea Plant, showing assorted apparatus and equipment used to produce Urea, a water-soluble powder form of carbonic acid frequently used as a…

Two views of the exterior of the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory facility located at American University near Washington, D.C. The Fixed Nitrogen Research Laboratory (F.N.R.L.) was…

Two views of the exterior of the Fixed Nitrogen Research Laboratory facilities located at American University near Washington, D.C. The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American…

General view of F.F. Robey at work in the carpenter shop at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory showing assorted machinery and apparatus.

The Fixed Nitrogen Research Laboratory…

Two views of an exhibition display concerning the work of the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The display includes assorted sample jars and a photograph…