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 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 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 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…

Close-up view of an alsike clover plant at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Notably, the root of the plant is growing from the pedicel (i.e. the stem…

General view of an apparatus used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory to determine the solubility of gases in water at various temperatures and pressures up to 1,000 atmospheres.
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General view of an apparatus used to investigate the Phase Rule in an iron-nitrogen system at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. First proposed by Josiah…

Four assorted views 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 an apparatus used to measure the effect of radiation on chemical reactions at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

General view of an apparatus used to measure the thermionic properties of catalyst surfaces at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In chemistry, the term…

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…

Close-up view of an apparatus used to obtain x-ray diffraction patterns at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory…

Close-up view of an apparatus used to study the photoelectric emissivity of catalysts at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Emissivity is a measure of the…

Close-up view of an apparatus used to study the absorption spectrum of ozone in visible and photographic infra red. This apparatus was used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

General view of an apparatus used to study the absorption spectrum of ozone in visible and photographic infra red. This apparatus was used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory…

Close-up view of an apparatus used to study the activation of gases by bombardment with positive ions at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed…

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 catalytic decomposition of ozone at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research…

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 an apparatus used for the spectroscopic study of the mechanism of nitrogen fixation in the electric arc at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

General view of an apparatus used to study the structure of molecules by means of the Raman effect using a three-glass prism Steinheil Spectrograph. This apparatus was used at the U.S. Department of Agriculture's Fixed…

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…

J.F. Shultz demonstrating use of an apparatus to test water gas catalysts at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. The term "water gas" commonly refers to…