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

soda \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.
   1. chem.
      a sodium oxide or hydroxide.
      b popularly, sodium carbonate or bicarbonate. sodium
          bicarbonate is also called baking soda
          1913 webster

   2. same as sodium, used in terms such as bicarbonate of
      soda.
      pjc

   3. same as soda water.
      pjc

   4. a non-alcoholic beverage, sweetened by various means,
      containing flavoring and supersaturated with carbon
      dioxide, so as to be effervescent when the container is
      opened; -- in different localities it is variously called
      also soda pop, pop, mineral water, and minerals.
      it has many variants. the sweetening agent may be natural,
      such as cane sugar or corn syrup, or artificial, such as
      saccharin or aspartame. the flavoring varies widely,
      popular variants being fruit or cola flavoring.
      pjc

   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.

   washing soda, sodium carbonate. colloq.
      1913 webster
see also:
solid baking soda sodium bicarbonate of soda soda water soda pop 
pop mineral water minerals caustic soda cooking soda 
sal soda sodium carbonate sodium soda alum soda ash 
salsola soda fountain soda lye soda niter nitratine 
soda salts soda waste alkali waste washing soda 

[2] : WordNet (r) 2.0

soda ash
     n : a sodium salt of carbonic acid; used in making soap powders
         and glass and paper syn: sodium carbonate, washing
         soda, sal soda, soda
see also:
sodium carbonate washing soda sal soda soda 

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