The Collaborative International Dictionary of English v.0.48:

Indoxyl \In*dox"yl\, n. [Indigo + hydroxyl.] (Chem.)
   A nitrogenous substance, C8H7NO, isomeric with oxindol,
   obtained as an oily liquid.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Oxindol \Ox*in"dol\, n. [Oxygen + indol.] (Chem.)
   A white crystalline nitrogenous substance (C8H7NO) of the
   indol group, obtained by the reduction of dioxindol. It is a
   so-called lactam compound.
   [1913 Webster]