Bicarbonate of soda is a white powder which is used in baking to make cakes rise, and also as a medicine for your stomach. a chemical substance used especially in baking, and sometimes taken with water as a medicine = baking soda. or sodium bicarbonate or baking soda Inorganic compound, white, crystalline salt of sodium, chemical formula NaHCO3. It is a weak base and dissociates into water and carbon dioxide gas as it dissolves in the presence of hydrogen ions. In addition to household uses as an antacid, cleaner, and deodorizer, it is used in manufacturing effervescent salts and beverages and baking powder. Industrial uses include production of other sodium salts, treatment of wool and silk, and use in pharmaceuticals, sponge rubber, fire extinguishers, cleaners, lab reagents, mouthwash, and gold and platinum plating