In alkaline solution manganese ions react with formaldoxime to form an orange-red complex. (Reaction principle analogous to DIN 38406-E2) --
Natural waters contain manganese in the divalent, soluble form as well as in colloidal tri- and tetravalent states. Valencies are interchanged by oxidation-reduction reactions taking place in the water. The test procedure determines all oxidation states of manganese.