Carbonated water is water into which carbon dioxide gas under pressure has been dissolved, either by technology or by a natural geologic source. Many kinds of water are carbonated, including sparkling mineral water, club soda, sparkling water or 'seltzer water' (US), tonic water, and soda water. Mineral water, club soda and soda water typically contain dissolved minerals such as potassium bicarbonate, sodium bicarbonate, or potassium sulfate which are meant to enhance its flavor, though sparkling water is water combined only with carbon dioxide with no other additives. Tonic water includes quinine. Carbonation is the process that causes the water to become effervescent. All forms of carbonated water are available in ready-to-drink bottles and cans but some can also be prepared at home with a soda maker.