Chem.
1. Also called soda ash . an anhydrous, grayish-white, odorless, water-soluble powder, Na 2 CO 3 , usually obtained by the Solvay process and containing about 1 percent of impurities consisting of sulfates, chlorides, and bicarbonates of sodium: used in the manufacture of glass, ceramics, soaps, paper, petroleum products, sodium salts, as a cleanser, for bleaching, and in water treatment.
2. Also called sal soda, soda, washing soda . the decahydrated form of this salt, Na 2 CO 3 ·10H 2 O, used similarly.
3. the monohydrated form of this salt, Na 2 CO 3 ·H 2 O, used similarly, esp. in photography.
[ 1865-70 ]