Abstract
Properties of carminic acid, a colorant extracted from the dried female Coccid insect, and its aluminum complexes in aqueous solution were determined by spectrophotometric methods. Carboxyl and hydroxyl groups in carminic acid show acidic characteristics. The three apparent dissociation constants $(K_{a})$ of carminic acid were determined and the absorption spectra for the different dissociation species were demonstrated. Aluminum could form 1:1 and 2:1 complex with carminic acid in aqueous solution. Apparent formation constants $(K_{f})$ for the formation of each of the complexes were determined.
