Source : Webster's Revised Unabridged Dictionary (1913)

Euthiochroic \Eu`thi*o*chro"ic\, a. [Gr. ? well + ? sulphur + ?
   color.] (Chem.)
   Pertaining to, or denoting, an acid so called.

   {Euthiochroic acid} (Chem.), a complex derivative of
      hydroquinone and sulphonic (thionic) acid. -- so called
      because it contains sulphur, and forms brilliantly colored
      (yellow) salts.