Vol·a·tile a.
 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 aeriform 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.


 Al·ka·li n.; pl. Alkalis or Alkalies
 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.
 3. Soluble mineral matter, other than common salt, contained in soils of natural waters. [Western U. S.]
 Fixed alkalies, potash and soda.
 Vegetable alkalies. Same as Alkaloids.
 Volatile alkali, ammonia, so called in distinction from the fixed alkalies.

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 am·mo·ni·a n.  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.

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