Source : Webster's Revised Unabridged Dictionary (1913)

Sulphindigotic \Sulph*in`di*got"ic\, a. (Chem.)
   Of, pertaining to, or designating, a sulphonic acid obtained,
   as a blue solution, by dissolving indigo in sulphuric acid;
   -- formerly called also {cerulic sulphuric} acid, but
   properly called {indigo-disulphonic acid}.