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.
Joseph Priestley first discovered a method of impregnating water with carbon dioxide when he suspended a bowl of water above a beer vat at a local Leeds brewery. The air blanketing the fermenting beer -- called variously 'fixed air' and 'mephitic air' -- was known to kill mice suspended in it. Priestley found water thus treated had a pleasant taste and he offered it to friends as a refreshing drink. In 1772 Priestley published a paper entitled Impregnating Water with Fixed Air in which he describes dripping oil of vitriol (or sulfuric acid as it is now called) onto chalk to produce carbon dioxide gas, and encouraging the gas to dissolve into an agitated bowl of water.
In 1771 Swedish chemistry professor Torbern Bergman independently invented a similar process to make carbonated water. Frugal yet ill, he was trying to reproduce naturally-effervescent spring waters thought at the time to be beneficial to health.
Today, carbonated water is made by passing pressurized carbon dioxide through water. The pressure increases the solubility and allows more carbon dioxide to dissolve than would be possible under standard atmospheric pressure. When the bottle is opened, the pressure is released, allowing the gas to come out of the solution, thus forming the characteristic bubbles.
Carbonated water is reputed to be good for removing stains, for example coffee stains from mugs, or stains from silver. It is said that red wine stains can be prevented from setting by sprinkling table salt on the stain and then applying liberal amounts of carbonated water.
Seltzer water was once commonly sold in small bottles with a metal handle on the side to control the dispensing of the contents (pictured at right). Since the carbonation in the water pressurizes the seltzer bottle, the liquid is propelled out as a stream. These bottles, along with the cream pie, became a common slapstick comedy prop favored by clowns, vaudeville performers, and The Three Stooges.
Soft drinks are often based on flavored carbonated water.
