- indigo-disulphonic acid
- 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}. [1913 Webster]
The Collaborative International Dictionary of English. 2000.