Naphthol

n.
  1. Any one of a series of hydroxyl derivatives of naphthalene, analogous to phenol. In general they are crystalline substances with a phenol (carbolic) odor.
    2. Naphthol blue, Naphthol orange, Naphthol yellow (Chem.),
    brilliant dyestuffs produced from certain complex nitrogenous derivatives of naphthol or naphthoquinone.