naphthol orange

from The Collaborative International Dictionary of English v.0.48

Naphthol \Naph"thol\, n. [Naphthalene + -ol.] (Chem.)
   Any one of a series of hydroxyl derivatives of naphthalene,
   analogous to phenol. In general they are crystalline
   substances with a phenol (carbolic) odor.
   [1913 Webster]

   {Naphthol blue}, {Naphthol orange}, {Naphthol yellow}
      (Chem.), brilliant dyestuffs produced from certain complex
      nitrogenous derivatives of naphthol or naphthoquinone.
      [1913 Webster]