Analytically important, strongly chelating anthraquinones and their derivatives were studied by d.c. polarography, cyclic voltammetry and micro-coulometry to investigate their redox characteristics. All 18 substances were reduced in a two-electron reversible or quasi-reversible process in both aqueous and 75% ethanolic solutions. Depending on pH and the medium, single or double polarographic reduction waves appeared, which were diffusion controlled, although in some instances adsorption pre-waves were also observed. This behaviour is similar to the known behaviour of simpler quinone systems. The variation of the Ilkovič coefficient and half-wave potential with pH was studied in detail to investigate the acid-base behaviour of the species involved in the reduction process. As a result, it was possible to describe the reduction mechanism of the anthraquinones involved.

A number of new pK values were determined and others confirmed. Attempts to find linear free energy relationships were generally unsuccessful.