noun
: a sodium salt of carbonic acid: as
a.
(1) : the hygroscopic crystalline anhydrous normal salt Na 2 CO 3 that is moderately soluble in cold water and gives a strongly alkaline reaction, that was originally obtained from the ash of sea plants but is now usually produced by the Solvay process in light and dense forms, and that is used chiefly in making glass, soap powders and soap builders, in water treatment, in the manufacture of pulp and paper, and in the manufacture of sodium hydroxide and other chemicals — called also soda ash ; compare leblanc process
(2) : the crystalline monohydrate Na 2 CO 3 .H 2 O found in nature as thermonatrite and used similarly to the anhydrous salt in photography and medicine
(3) : the efflorescent crystalline decahydrate Na 2 CO 3 .10H 2 O found in nature as natron but usually made artifically by crystallization and used chiefly in washing and bleaching textiles — called also sal soda, soda, washing soda
b. : sodium bicarbonate
c. : sodium sesquicarbonate