General view of J.F. Shultz demonstrating an apparatus used to analyze the effect of phosphine upon ammonia catalysts at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

General view of Mrs. M.K. Murray demonstrating use of a nitrometer, an apparatus used to determine the amount of nitrogen or nitrogen compounds in a substance or mixture, at the U.S. Department of Agriculture's Fixed…

General view of R.J. Connor photographing the spectrum of active nitrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In chemistry, "spectrum" commonly refers…

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…

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…

General view of V.L. Gaddy demonstrating use of compressors at the Fixed Nitrogen Research Laboratory's Urea Plant. In the production of fertilizer, liquid carbon dioxide and liquid ammonia are commonly combined under…

General view of W.E. Kuentzel demonstrating use of an apparatus for the removal of carbon monoxide from water gas by means of preferential combustion at the U.S. Department of Agriculture's Fixed Nitrogen Research…

General view of the exterior of the water gas generator at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The term "water gas" commonly refers to the mixture of…

General view of V.L. Gaddy demonstrating an apparatus used to create a constant-temperature bath to determine the equilibrium of Urea, a water-soluble powder form of carbonic acid frequently used as a fertilizer and…

General view of the ammonia-carbon dioxide pump and Urea autoclave used 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 an apparatus used to oxidize ammonia 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…

R.A. Nelson (left) and E.S. Lamar (right) demonstrating an apparatus used to study the decomposition of ammonia on hot catalyst surfaces by means of the coated strip method. This apparatus was used at the U.S.…

Close-up view of an apparatus used to study the decomposition of ammonia on hot catalyst surfaces by means of the coated strip method. This apparatus was used at the U.S. Department of Agriculture's Fixed Nitrogen…

General view of the construction and calibration of an apparatus used to analyze the decomposition of ammonia on hot surfaces at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in…

General view of an apparatus used to grow plants under sterile conditions 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 C.A. Black 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. 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 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…

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 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…

General view of numbered test tube samples from the Ammonia-(Urea-Water) system at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Urea is a water-soluble powder form…

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 an apparatus used to study the absorption of nitrogen oxides by silica gel at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

Two views of an apparatus used to determine the hygroscopicity of fertilizer materials and mixtures at the the Arlington Experimental Farm in Arlington, Virginia. The individual visible in the first photograph is…