Salicylic Acid, or ORTHO-OXYBENZOIC ACID, is represented by the chemical formula C6H(OH)CO2H, and consists of benzoic acid in which one of the hydrogen atoms has been replaced by the group OH (hydroxyl). It occurs naturally in the buds of some species of spiraea, and also combined with methyl alcohol in oil of wintergreen. It may be also prepared artificially by many chemical reactions, as by the action of carbonic acid and sodium on carbolic acid.
C6H5ONa + CO2H4(OH)CO2Na.
It forms four-sided prisms which melt at 156°. It is only slightly soluble in cold water, but readily in hot, so that it can be easily crystallised. If heated slowly it sublimes, but if heated rapidly decomposes. It is readily recognised by the production of a deep violet colour when ferric chloride is added to its aqueous solution. It is a good antiseptic and is used as such in surgery, while it, also finds other medicinal applications.