sulphindigotic acid

== English == === Noun === sulphindigotic acid (uncountable) (obsolete, organic chemistry) A sulfonic acid obtained by dissolving indigo in sulfuric acid. It was once used as a dye. ==== Derived terms ==== === References === “sulphindigotic”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.