Acid-base, spectrophotometric, and colorimetric properties of 1,2-dihydroxyantraquinonone-3-sulfoacid (Alizarin Red S)

Acid-base, spectrophotometric, and colorimetric properties of 1,2-dihydroxyantraquinonone-3-sulfoacid (Alizarin Red S, ARS ) have been studied in aqueous solutions at pH 3–13. Equations of calibration curves have been obtained for the dependences of absorbance and colorimetric functions ( CF ) on the ARS concentration. Molar absorption coefficients and CF have been determined. Dissociation constants of ARS have been determined using a spectrophotometric technique in its computational and graphical versions at an ionic strength from 0.1 to 0.5.