The Collaborative International Dictionary of English v.0.48:

Volatile \Vol"a*tile\, a. [F. volatil, L. volatilis, fr. volare
   to fly, perhaps akin to velox swift, E. velocity. Cf.
   Volley.]
   1. Passing through the air on wings, or by the buoyant force
      of the atmosphere; flying; having the power to fly. [Obs.]
      [1913 Webster]

   2. Capable of wasting away, or of easily passing into the
      aeriform state; subject to evaporation.
      [1913 Webster]

   Note: Substances which affect the smell with pungent or
         fragrant odors, as musk, hartshorn, and essential oils,
         are called volatile substances, because they waste away
         on exposure to the atmosphere. Alcohol and ether are
         called volatile liquids for a similar reason, and
         because they easily pass into the state of vapor on the
         application of heat. On the contrary, gold is a fixed
         substance, because it does not suffer waste, even when
         exposed to the heat of a furnace; and oils are called
         fixed when they do not evaporate on simple exposure to
         the atmosphere.
         [1913 Webster]

   3. Fig.: Light-hearted; easily affected by circumstances;
      airy; lively; hence, changeable; fickle; as, a volatile
      temper.
      [1913 Webster]

            You are as giddy and volatile as ever. --Swift.
      [1913 Webster]

   Volatile alkali. (Old Chem.) See under Alkali.

   Volatile liniment, a liniment composed of sweet oil and
      ammonia, so called from the readiness with which the
      latter evaporates.

   Volatile oils. (Chem.) See Essential oils, under
      Essential.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Alkali \Al"ka*li\ (?; 277), n.; pl. Alkalis or Alkalies. [F.
   alcali, ultimately fr. Ar. alqal[imac] ashes of the plant
   saltwort, fr. qalay to roast in a pan, fry.]
   1. Soda ash; caustic soda, caustic potash, etc.
      [1913 Webster]

   2. (Chem.) One of a class of caustic bases, such as soda,
      potash, ammonia, and lithia, whose distinguishing
      peculiarities are solubility in alcohol and water, uniting
      with oils and fats to form soap, neutralizing and forming
      salts with acids, turning to brown several vegetable
      yellows, and changing reddened litmus to blue.
      [1913 Webster]

   3. Soluble mineral matter, other than common salt, contained
      in soils of natural waters. [Western U. S.]
      [Webster 1913 Suppl.]

   Fixed alkalies, potash and soda.

   Vegetable alkalies. Same as Alkaloids.

   Volatile alkali, ammonia, so called in distinction from the
      fixed alkalies.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

ammonia \am*mo"ni*a\ ([a^]m*m[=o]"n[i^]*[.a]), n. [From sal
   ammoniac, which was first obtaining near the temple of
   Jupiter Ammon, by burning camel's dung. See Ammoniac.]
   (Chem.)
   A gaseous compound of hydrogen and nitrogen, NH3, with a
   pungent smell and taste: -- often called volatile alkali,
   and spirits of hartshorn. It is very soluble in water,
   forming a moderately alkaline solution, and is used in
   aqueous solution as a household cleaning agent, such as for
   cleaning grease from glass.
   [1913 Webster + PJC] Ammoniac