Contribution to the solution chemistry and polarographic behaviour of anthrapurpurin complexan

The reduction of the 1,2,7-trihydroxyanthraquinone-3-methylamino-N,N-diacetic acid at dropping mercury electrode has been investigated. The reduction involves two electrons as well as either one or two hydrogen ions depending on the pH. Two alternative reaction mechanisms are proposed. Five acid-dissociation constants have been determined by potentiometric and spectrophotometric methods. A sequence for the dissociation of the protons is proposed. Thermal gravimetric and differential analysis of the anhydrous and dihydrated reagent are reported.