Wikipedia Article About Soda water on Wikipedia Carbonated water, also known as soda water, sparkling water, or seltzer water, is plain water into which carbon dioxide gas has been dissolved. The process of dissolving carbon dioxide gas is called carbonation. It results in the formation of carbonic acid (which has the chemical formula H2CO3). Club soda may be identical to plain carbonated water or it may contain a small amount of table salt, sodium citrate, sodium bicarbonate, potassium bicarbonate, potassium sulfate, or disodium phosphate, depending on the bottler.