General view of an apparatus used to study the thermal dissociation of sodium cyanide at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Thermal dissociation is…

General view of a thermostat apparatus used to measure rates of reaction 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 apparatus used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory to introduce silica gel into an arc process. In the early 20th century, the arc process, in which electric…

General view of an apparatus used to measure vapor pressures in the study of Urea synthesis at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In the production of…

General view of an apparatus used to study the relative activity of potassium ions and electrons in the synthesis of ammonia from nitrogen and hydrogen gas at the U.S. Department of Agriculture's Fixed Nitrogen Research…

General view of an apparatus used to study the thermal decomposition of ammonia of the surface of tungsten, molybdenum, nickel, and iron catalysts at the U.S. Department of Agriculture's Fixed Nitrogen Research…

Mr. Hetherington demonstrating the barometers and potentiometer used for temperature control at the High-Pressure Laboratory, part of the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory facilities…

Three views of the carbon monoxide generator and compressor used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The individual visible in the second and third…

General view of two compression and high-pressure storage cylinders used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Part of a hand-operated booster connected…

General view of compressor used in the carbon dioxide refrigeration system at the Fixed Nitrogen Research Laboratory's High-Pressure Laboratory. The individual present in the photograph is identified as Mr. Tremearne.
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Close-up view of a decomposition chamber used to facilitate the thermal decomposition of ammonia on tungsten, molybdenum, nickel, and iron catalysts at the U.S. Department of Agriculture's Fixed Nitrogen Research…

General view of Dr. Leatherman using an apparatus to determine the amount of inert gas present in nitrogen made from the fractionation of liquid air at the Fixed Nitrogen Research Laboratory's High-Pressure Laboratory. …

General view of Dr. Leatherman using an apparatus to measure traces of inert gas and air in nitrogen at the Fixed Nitrogen Research Laboratory's High-Pressure Laboratory.

The Fixed Nitrogen Research Laboratory…

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.…

General view of assorted apparatus used in the Fixed Nitrogen Research Laboratory's High-Pressure Laboratory, including a hydraulic pressure pump, piston-type gauges, high-pressure booth, and valve manifold. The…

General view of Mr. L. Pinck demonstrating use of a liquid air condenser employed for low-temperature distillations at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.
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General view of the apparatus used to measure gas volumes in order to make compressibility determinations at the High-Pressure Laboratory, part of the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

General view of a test tube used to study the activity of potassium ions and electrons in the activation of nitrogen gas and hydrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

General view of the thermostat and apparatusused to measure vapor pressures in the study of Urea synthesis at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Urea is a…

General view of a thermostat and equipment used to determine the compressibility of gas at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In chemistry,…

General view of the thermostat and other equipment used to measure gas volumes in order to make compressibility determinations at the High-Pressure Laboratory, part of the U.S. Department of Agriculture's Fixed…

General view of the thermostat, apparatus, and analytical train used to measure vapor pressures in the study of Urea synthesis at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

Two aerial views of facilities believed to be associated with the U.S. Department of Agriculture.

General view of an unidentified apparatus, possibly a pump or compressor, used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research…