Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A colorless, highly flammable gaseous element, the lightest of all gases and the most abundant element in the universe, used in the production of synthetic ammonia and methanol, in petroleum refining, in the hydrogenation of organic materials, as a reducing atmosphere, in oxyhydrogen torches, and in rocket fuels. Atomic number 1; atomic weight 1.00794; melting point -259.14°C; boiling point -252.8°C; density at 0°C 0.08987 gram per liter; valence 1. See Table at element.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The lightest chemical element (symbol H) with an atomic number of 1 and atomic weight of 1.00794.
  • n. Molecular hydrogen (H2), a colourless, odourless and flammable gas at room temperature.
  • n. An atom of the element.
  • n. A sample of the element.

from the GNU version of the Collaborative International Dictionary of English

  • n. A gaseous element, colorless, tasteless, and odorless, the lightest known substance, being fourteen and a half times lighter than air (hence its use in filling balloons), and over eleven thousand times lighter than water. It is very abundant, being an ingredient of water and of many other substances, especially those of animal or vegetable origin. It may by produced in many ways, but is chiefly obtained by the action of acids (as sulphuric) on metals, as zinc, iron, etc. It is very inflammable, and is an ingredient of coal gas and water gas. It is standard of chemical equivalents or combining weights, and also of valence, being the typical monad. Symbol H. Atomic weight 1.

from The Century Dictionary and Cyclopedia

  • n. Chemical symbol, H. One of the elementary substances, existing as a colorless, tasteless, and inodorous gas.
  • n. H2S, a colorless inflammable gas having a sweetish taste and an exceedingly fetid smell resembling rotten eggs. It is extremely poisonous when inhaled. It has feeble acid properties, and its compounds with bases are called sulphids. It occurs in the emanations of volcanoes, and is evolved when animal or vegetable tissue containing sulphur decays. It also occurs in mineral springs, being liberated by the reduction of gypsum or other sulphates through the action of a microbe.
  • n. Hydrogen compounds with strongly electronegative elements or radicals, easily exchanging hydrogen for strongly electropositive elements or radicals to form salts, are the same as acids: as hydrogen chlorid (hydrochloric acid), hydrogen sulphate (sulphuric acid), etc.

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

  • n. a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe

Etymologies

French hydrogène : Greek hudro-, hydro- + French -gène, -gen.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From French hydrogène, coined by Louis-Bernard Guyton de Morveau, from Ancient Greek ὕδωρ (hudōr, "water") + γεννάω (gennaō, "I bring forth"). (Wiktionary)

Examples

  • ~ New 'biofuel cell' produces electricity from hydrogen in plain air -- "A pioneering “biofuel cell” that produces electricity from ordinary air spiked with small amounts of hydrogen offers significant potential as an inexpensive and renewable alternative to the costly platinum-based fuel cells that have dominated discussion about the “hydrogen economy” of the future, British scientists reported here today."

    Speedlinking 3/27/07

  • But if we consider hydrogen as a gasiform metal, we naturally arrive at the conclusion that _water is the hydroxide of this gasiform metal_, that is _hydrogen hydroxide_, while gaseous hydrochloric and hydrosulphuric acids would be looked upon as respectively the chloride and the sulphide of the metal hydrogen.

    Scientific American Supplement No. 822, October 3, 1891

  • Carbon also escapes into the air, combined with hydrogen, in the form of _carburetted hydrogen_ or _marsh-gas_ (CH_4), a product of the decomposition of organic matter in the presence of a large quantity of water.

    Manures and the principles of manuring

  • I believe it was linzloo08 who said that, in referencing the fact that the sun will stop shining when the hydrogen is all gone.

    Think Progress » Sarah Palin calls global warming studies ‘snake oil science.’

  • We already know that the poles of the Moon contain elevated hydrogen content (the rare element on the Moon); this hydrogen is there regardless of its physical form, either as water ice or as solar wind protons.

    Back to the Moon We Go - NASA Watch

  • This is the pipe through which we convey this particular gas, which we call hydrogen, and which you shall know all about the next time we meet.

    The Chemical History of a Candle

  • The atoms of what we call hydrogen or oxygen may well turn out to be worlds, as the stars are which make atoms for astronomy.

    The Life of Reason

  • "This is a result of what we call the hydrogen effect," says Patrik Fors, who will defend his thesis in nuclear chemistry at Chalmers on Friday.

    PhysOrg.com - latest science and technology news stories

  • As everyone has pointed out, hydrogen is a very tricky substance to store, and that is why one of the cheaper methods is to use fossil fuels.

    Hydrogen Cars, Arnold Kling | EconLog | Library of Economics and Liberty

  • I am increasingly of the view that hydrogen is kinda like the emperor who has no clothes.

    Hydrogen Cars, Arnold Kling | EconLog | Library of Economics and Liberty

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