Lactart is the namesake of a family of sour beverages, first popular in the late 19th century, that don't rely on lemons or limes. Instead of citric acid, soda-fountain lactarts look to the "acid of milk" — that is, lactic acid — but don't taste like dairy products. Compared with a citric-acid drink of the same flavor, however, a lactart can fairly be described as less "sharp." Shown: an orange lactart ($3).
Hamilton's Soda Fountain & Luncheonette
51 Bank St. (at West 4th St.), Manhattan