Salicylic acid or ortho-hydroxybenzoic acid is either a white, crystalline powder or white to colorless crystal needles that are difficult to dissolve in cold water and easily soluble in 96% ethanol. It is more soluble in hot water. Salicylic acid has a sweet and sour taste. It occurs naturally in the form of derivatives in many plants. It belongs to the phenols and the carboxylic acid. Salicylic acid has antimicrobial (fungus and bacteria), analgesic and anti-inflammatory properties.
Salicylic acid is used to produce dyes and fragrances and acetylsalicylic acid (ASA, also known under the brand name aspirin). The product can form an ester with organic acids, salicylic acid then acting as an alcohol in the reaction. In addition, salicylic acid is used in the cosmetics and perfume industry as anti-rheumatic agents in bath additives, ointments or creams, as well as fragrances and UV filters in sunscreens. The wide range of applications is underlined by the possibility of using it as a flux for soft soldering. Furthermore, bromination with elemental bromine in glacial acetic acid produces an acid, the salt of which can be used as a fungicide and bactericide.