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Subject Tubes--Testing Remove constraint Subject: Tubes--Testing

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    • 1970s

    Close-up view of chemist Francis Ptak holding a rack of Nessler tubes at a Gascoyne Laboratory facility located in Baltimore, Maryland. A Perkin-Elmer automated, multi-element spectrophotometer is visible in the…

    • 1952

    General view of an unidentified employee working with assorted test tubes in the Dow Chemical Company's Biological Chemical Laboratory. The laboratory commonly conducted research and testing related to the development…

    • 1930-Jan-08

    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…

    • 1928-Aug-21

    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…

    • 1927-Jul-26

    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…