- a solid appearing reddish-orange as crystals and brownish-yellow as powder, C14H8O4, one of the earliest known dyes, formerly obtained in its natural state from madder and now derived from anthraquinone: used chiefly in the synthesis of other dyes.
- a brownish-yellow powder or orange-red crystalline solid used as a dye and in the manufacture of other dyes. Formula: C 6 H 4 (CO) 2 C 6 H 2 (OH) 2
