Figure 4. a: Reversible oxidation of alizarin: 2-electron, 2-proton process, b: Nucleophilic attack by water followed by further oxidation and tautomerism [6]

From

Monitoring pH Using Alizarin-modified Commercial Screen-printed Electrodes

Achim Habekost

World Journal of Chemical Education. 2020, 8(4), 163-169 doi:10.12691/wjce-8-4-4