[1] : The Collaborative International Dictionary of English v.0.48

hydrogen \hy"drogen\, n. hydro-, 1 + -gen: cf. f.
   hydrog`ene. so called because water is generated by its
   combustion. see hydra. chem.
   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.
   1913 webster

   note: although a gas, hydrogen is chemically similar to the
         metals in its nature, having the properties of a weak
         base. it is, in all acids, the base which is replaced
         by metals and basic radicals to form salts. like all
         other gases, it is condensed by great cold and pressure
         to a liquid which freezes and solidifies by its own
         evaporation. it is absorbed in large quantities by
         certain metals esp. palladium, forming alloy-like
         compounds; hence, in view of quasi-metallic nature, it
         is sometimes called hydrogenium. it is the typical
         reducing agent, as opposed to oxidizers, as oxygen,
         chlorine, etc.
         1913 webster

   bicarbureted hydrogen, an old name for ethylene.

   carbureted hydrogen gas. see under carbureted.

   hydrogen dioxide, a thick, colorless liquid, h2o2,
      resembling water, but having a bitter, sour taste,
      produced by the action of acids on barium peroxide. it
      decomposes into water and oxygen, and is manufactured in
      large quantities for an oxidizing and bleaching agent.
      called also oxygenated water.

   hydrogen oxide, a chemical name for water, h?o.

   hydrogen sulphide, a colorless inflammable gas, h2s,
      having the characteristic odor of bad eggs, and found in
      many mineral springs. it is produced by the action of
      acids on metallic sulphides, and is an important chemical
      reagent. called also sulphureted hydrogen.
      1913 webster
see also:
hydra hydrogenium bicarbureted hydrogen carbureted hydrogen gas carbureted hydrogen dioxide 
h2o2 oxygenated water hydrogen oxide hydrogen sulphide h2s 
sulphureted hydrogen 

[2] : The Collaborative International Dictionary of English v.0.48

ethylene \eth"ylene\ e^th"i^l=en, n. from ethyl.
   chem.
   a colorless, gaseous hydrocarbon, c2h4, forming an
   important ingredient of illuminating gas, and also obtained
   by the action of concentrated sulphuric acid in alcohol. it
   is an unsaturated compound and combines directly with
   chlorine and bromine to form oily liquids dutch liquid, --
   hence called olefiant gas. called also ethene, elayl,
   and formerly, bicarbureted hydrogen.
   1913 webster

   ethylene series chem., the series of unsaturated
      hydrocarbons of which ethylene is the type, and
      represented by the general formula cnh2n.
      1913 webster
see also:
ethyl c2h4 olefiant gas ethene elayl bicarbureted hydrogen 
ethylene series cnh2n 

Hydrogen >> H Words
Hydrogen, definition of term: Hydrogen
hydrogen_pag1.html

Hydrogen Peroxi >> H Words
Hydrogen Peroxi, definition of term: Hydrogen Peroxi
hydrogen+peroxi_pag1.html

Hydrogen Sulfid >> H Words
Hydrogen Sulfid, definition of term: Hydrogen Sulfid
hydrogen+sulfid_pag1.html

Hydrogen Dioxid >> H Words
Hydrogen Dioxid, definition of term: Hydrogen Dioxid
hydrogen+dioxid_pag1.html

Hydrogen Cyanid >> H Words
Hydrogen Cyanid, definition of term: Hydrogen Cyanid
hydrogen+cyanid_pag1.html

Hydrogen Atom >> H Words
Hydrogen Atom, definition of term: Hydrogen Atom
hydrogen+atom_pag1.html

Hydrogen Bomb >> H Words
Hydrogen Bomb, definition of term: Hydrogen Bomb
hydrogen+bomb_pag1.html

Hydrogen Ion Co >> H Words
Hydrogen Ion Co, definition of term: Hydrogen Ion Co
hydrogen+ion+co_pag1.html