Source : Webster's Revised Unabridged Dictionary (1913)

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.]

   2. Capable of wasting away, or of easily passing into the
      a["e]riform state; subject to evaporation.

   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.

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

            You are as giddy and volatile as ever. --Swift.

   {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}.

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

   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.

   {Fixed alkalies}, potash and soda.

   {Vegetable alkalies}. Same as {Alkaloids}.

   {Volatile alkali}, ammonia, so called in distinction from the
      fixed alkalies.