a. Chem. [ad. F. sulfoindigotique (1832): see SULPHO- and INDIGOTIC.] = SULPHINDIGOTIC. Hence Sulpho-indigotate. So Sulphoindylic acid.
1838. T. Thomson, Chem. Org. Bodies, 198. To obtain the sulpho-indigotic acid we dissolve the sulpho-indigotate of ammonia in water, and precipitate by acetate of lead.
1855. Ogilvie, Dict., Suppl., Sulphoindilic acid, a blue acid formed by the action of sulphuric acid upon indigo.
1881. Cleland, Evol., etc., v. 132. Sulpho-indigotate of soda.
