A spectroscopic investigation of the behavior of anthraquinone in sulfuric acid and oleum

Dissolution of anthraquinone in concentrated sulfuric acid and in oleum is accompanied by a coloration of the solution. It has been observed [1] that in 92–96% sulfuric acid anthraquinone gives a yellow solution, while in 20% oleum the color is red. The assumption has been made [2] that in the first case one of the carbonyl groups of the anthraquinone reacts with the acid, while in the second case both undergo reaction.