Salicylic acid the OH group is "ortho" to the carboxyl group. It is also known as 2-hydroxybenzoic acid. It is poorly soluble in water (2 g/L at 20 °C). Aspirin (acetylsalicylic acid or ASA) can be prepared by the esterification of the phenolic hydroxyl group of salicylic acid with the acetyl group from acetic anhydride or acetyl chloride. Salicylic acid can also be prepared using the Kolbe-Schmitt reaction. Salicylic acid is used as a food preservative, a bactericidal and an antiseptic. Sodium salicylate is a useful phosphor in the vacuum ultraviolet spectral range, with nearly flat quantum efficiency for wavelengths between 10
History of aspirin preparations became a standard part of the "materia medica" of Western medicine beginning at least with the Greek physician Hippocrates in the fifth century BCE; he recommended chewing on willow bark to relieve pain or fever, and drinking tea made from it to relieve pain during childbirth. The Roman encyclopedist Celsus, in his "De Medicina" of ca. 30 AD, suggested willow leaf extract to treat the four signs of inflammation: redness, heat, swelling and pain. Willow treatments also appeared in Dioscorides's "De Materia Medica", and Pliny the Elder's "Natural History". By the time of Galen, willow bark was commonly used