naphthol (năf´thôl), C10H7OH, either of two crystalline monohydric alcohols. The naphthols are position isomers, differing in the location of the hydroxyl group, -OH, on the carbon skeleton of naphthalene; α-naphthol is 1-hydroxynaphthalene and β-naphthol is 2-hydroxynaphthalene: The naphthols have a number of similar properties. They melt at 95°C and 122°C and boil at 279°C and 285°C, respectively; both are soluble in alcohol and ether and slightly soluble in hot water. One way in which they differ is the form of their crystals—α-naphthol crystallizes in prisms and β-naphthol in plates. The naphthols are prepared by reacting naphthalene with sulfuric acid and hydrolyzing the resultant sulfate ester by heating it with sodium hydroxide solution. Both naphthols exhibit antiseptic properties. They are used in the synthesis of certain azo dyes and antioxidants for rubbers. Naphthol solutions are used in chemical analysis to detect the ferric ion; dissolved ferric ion turns an α-naphthol solution violet and turns a β-naphthol solution green.