General view of the gas purification rack, a component of an apparatus used to study the catalytic decomposition of ozone at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

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 the hydraulic pump used to perform steel corrosion tests 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 a laboratory facility and apparatus used to investigate the chemical activity evident in glow discharge at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

General view of an apparatus used to investigate the thermionic emission of positive ions from platinum films sputtered on glass at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

Close-up view of a lime glass tube, part of an apparatus used to investigate the thermionic emission from platinum films sputtered on glass at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

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…

View of the front 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 mercury arc…

General view of Mr. Olmstead. operating an ultrasonic oscillator used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Visible components of the oscillator include…

General view of the organic combustion furnace and train utilized 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.)…

Two views of the component parts of an apparatus used to grow higher plants in a sterile medium at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

M.C. Molstad demonstrating use of an apparatus for the removal of carbon dioxide from water gas by means of scrubbing under pressure at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

General view of culture samples used for an experiment to determine if corn can secure its nitrogen from the air if grown in the presence of nitrogen-fixing bacteria. This experiment was conducted at the U.S.…

General view of culture samples used for an experiment to determine if corn growing under sterile conditions can use ammonia nitrogen. This experiment was conducted at the U.S. Department of Agriculture's Fixed Nitrogen…

Close-up view of a sterile culture of small phanerogams, also known as spermatophytes or seed plants, at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The…

R.A. Nelson (left) and Dr. C.H. Kunsman (right) demonstrating an apparatus used to study the decomposition of ammonia on catalyst surfaces at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

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…

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…

Two views of a thermocouple apparatus and assorted components, including a micro-spot welder and soldiering pencil, at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. …

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…

Close-up view of the thermostat used to maintain ammonia bubbles at sixty-five degrees Celsius during steel corrosion tests at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

Close-up view of an ultrasonic oscillator with a soil suspension and view of the driving transformer and oil bath containing piezoelectric quartz crystal. This oscillator was used at the U.S. Department of Agriculture's…

Close-up view of the Warburg-Barcroft microrespiration apparatus used to study bacterial nitrogen fixation at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The…

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