Apparatus used to analyze vapors emitted from the reaction of liquid carbon dioxide and liquid ammonia at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In the…

General view of an apparatus used to analyze micro quantities of gases at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research Laboratory…

An apparatus used to study thermal reactions in gases at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. A protective screen partially obscures the front of the…

An apparatus used to study the thermal reaction of acetylene and nitrogen 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 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 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 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…

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…

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 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 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…

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…

Apparatus used to determine vapor pressure of vapor emitted from the reaction of liquid carbon dioxide and liquid ammonia at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

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.
…

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…

Absorption chamber for nitrogen oxides used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. In this photograph, the chamber's casing has been removed to show the…

Three exterior views of unidentified buildings believed to be associated with the U.S. Department of Agriculture.

General view of an unidentified analytical apparatus and technician 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 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 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 an apparatus used to study the Bucher Process for the fixation of nitrogen at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Based on research…

View of a stirring machine designed at the Arlington Experimental Farm in Arlington, Virginia. Established by an act of Congress in April 1900, Arlington Farm served as the main field laboratory for the Bureau of Soils,…

General view of an apparatus used to facilitate the adsorption of silica gel and nitrogen oxide at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. Adsorption refers to…