\So"da\, n. [It., soda, in OIt., ashes used in making
glass, fr. L. solida, fem. of solidus solid; solida having
probably been a name of glasswort. See {Solid}.] (Chem.)
(a) Sodium oxide or hydroxide.
(b) Popularly, sodium carbonate or bicarbonate.
{Caustic soda}, sodium hydroxide.
{Cooking soda}, sodium bicarbonate. [Colloq.]
{Sal soda}. See {Sodium carbonate}, under {Sodium}.
{Soda alum} (Min.), a mineral consisting of the hydrous
   sulphate of alumina and soda.
{Soda ash}, crude sodium carbonate; -- so called because
   formerly obtained from the ashes of sea plants and certain
   other plants, as saltwort ({Salsola}). See under {Sodium}.
{Soda fountain}, an apparatus for drawing soda water, fitted
   with delivery tube, faucets, etc.
{Soda lye}, a lye consisting essentially of a solution of
   sodium hydroxide, used in soap making.
{Soda niter}. See {Nitratine}.
{Soda salts}, salts having sodium for the base; specifically,
   sodium sulphate or Glauber's salts.
{Soda waste}, the waste material, consisting chiefly of
   calcium hydroxide and sulphide, which accumulates as a
   useless residue or side product in the ordinary Leblanc
   process of soda manufacture; -- called also {alkali
   waste}.
{Soda water}, originally, a beverage consisting of a weak
   solution of sodium bicarbonate, with some acid to cause
   effervescence; now, in common usage, a beverage consisting
   of water highly charged with carbon dioxide (carbonic
   acid). Fruit sirups, cream, etc., are usually added to
   give flavor. See {Carbonic acid}, under {Carbonic}.
{Washing soda}, sodium carbonate. [Colloq.]