from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The most abundant isotope of hydrogen, H-1, having one proton in the nucleus.

from The Century Dictionary.

  • noun A genus of polypetalous trees of the order Burseraceæ and tribe Bursereæ.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun physics The lightest and most common isotope of hydrogen, having a single proton and no neutrons - 11H
  • noun An atom of this isotope.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun genus of chiefly tropical American trees having fragrant wood and yielding gum elemi


from Wiktionary, Creative Commons Attribution/Share-Alike License

from Ancient Greek πρῶτος (prōtos, "first") + -ium


  • Urey calls heavy hydrogen deuterium and ordinary hydrogen protium.

    Nobel Prize in Chemistry 1934 - Presentation Speech

  • Baltic; they must have perished miserably but for the discovery of a new source of protium.

    City of Endless Night

  • The Emperor nodded to the Chief of the Chemical Staff who arose and read the report of my solution of the protium problem.

    City of Endless Night

  • The voice was speaking monotonously and the words I heard were the words of the protium formulas, the false ones I had given the Chemical Staff.

    City of Endless Night

  • But I wanted power; and, with the secret of protium extraction in my possession, I would have control of life or death over three hundred million men.

    City of Endless Night

  • Sending their submarines thence in search of platinum ores they had not found platinum but a limited supply of ore containing the even more valuable protium.

    City of Endless Night

  • The Staff discussed this and has assigned you to original research for the finding of a better method of the extraction of protium from the ore.

    City of Endless Night

  • After Russia had been won by the World Armies, the Germans for a time suffered chronic nitrogen starvation, as they depended on the protium derived from what remained of their agriculture and from the fisheries in the

    City of Endless Night

  • The original use of protium had, I found, been discovered late in the Twentieth Century when the protium ores of the

    City of Endless Night

  • All my ingredients were tested for the presence of extracted protium, lest I be trying to "salt the mine."

    City of Endless Night


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