General view of an unidentified worker sorting raw material, possibly ore or phosphate, at a Fixed Nitrogen Research Laboratory plant. The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American…

General view of an experimental blast furnace at a U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory plant. The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American University in…

Three views of the experimental blast furnace on a burden (a load, especially a heavy one) of phosphate at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory plant.

The Fixed Nitrogen Research…

Two views of the experimental blast furnace on a burden (a load, especially a heavy one) of phosphate at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory plant.

The Fixed Nitrogen Research…

Portrait of Dr. Henry G. Knight, Chief of the U.S. Department of Agriculture's Bureau of Chemistry & Soils.

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…

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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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 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…

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 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…

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…

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…

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…

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…

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…

Close-up view of an apparatus used to produce soft x-radiation 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.)…

General view of an apparatus for the study of equilibrium in the iron-water-iron oxide-hydrogen system at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed…

Close-up view of the assembly of an apparatus used for sterile cultures of taller green plants at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…