carbonated beverage, an effervescent drink that releases carbon dioxide under conditions of normal atmospheric pressure. Carbonation may occur naturally in spring water that has absorbed carbon dioxide at high pressures underground. It can also be a byproduct of fermentation, such as beer and some wines (see champagne). Many curative properties have been attributed to effervescent waters (e.g., aiding digestion and calming nerves), but few have been scientifically tested. The term seltzer once referred to the effervescent mineral water obtained from the natural springs near the village of Niederseltsers in SW Germany. Today, however, seltzer is simply well-filtered tap water with artificially added carbonation. Club soda is also artificially carbonated but contains other additives as well, including sodium bicarbonate, sodium chloride, sodium phosphate, sodium citrate, and sometimes light flavoring. Artificial carbonation was first introduced in 1767 by an Englishman, Joseph Priestley, and was commercialized in 1807 by Benjamin Silliman, a Yale Univ. chemistry professor, who bottled and sold seltzer water. After 1830, sweetened and flavored (lemon-lime, grape, orange) carbonated drinks became popular. In 1838, Eugene Roussel added a "soda counter" to his Philadelphia shop; by 1891, New York City had more soda fountains than bars. In 1886, John S. Pemberton, an Atlanta druggist seeking a headache and hangover remedy, added kola nut extract to coca extract and produced Coca-Cola. A pharmacist named Hires invented root beer in 1893. Today, heavily sweetened, carbonated drinks, or sodas, are among the most popular beverages in the world. In the last two decades, the introduction of diet drinks containing artificial sweeteners has increased sales of carbonated beverages. Annual Coca-Cola sales alone total more than a billion dollars, and sodas account for one-fourth of the annual sugar consumption in the United States.