[¦ȯr·thō ‚hī¦dräk·səl′an·əl·ən] (organic chemistry) C6H4NH2OH White crystals that turn brownish upon standing for some time; melts at 172-173°C, and will sublime upon more heating; soluble in cold water and benzene; used as a dye for hair and furs, and as a dye intermediate. Also known as ortho-aminophenol; oxammonium.