a. Chem. [ad. F. sulfo-purpurique (Dumas, 1836): see SULPHO- and PURPURIC.] Applied to an acid obtained by the action of sulphuric acid on indigo. Hence Sulphopurpurate.
1838. T. Thomson, Chem. Org. Bodies, 378.
1857. Miller, Elem. Chem., Org., viii. 531. Sulphopurpuric Acid … forms a blue solution in pure water. When acetate of potash is added to this liquid it gives a purple precipitate of sulphopurpurate of potash.
1881. Encycl. Brit., XII. 844/1.
