Effect of cyanide ion on manganese (III) triethanolamine complex

Abstract

The reaction of cyanide ion with manganese (III) triethanolamine complex in alkaline solution was studied by polarography and spectrophotometry in visible and ultraviolet region.
Manganese (III) triethanolamine complex (green) is reduced gradually to manganese(II) triethanol-amine complex (colourless) in the presence of a large quantity of cyanide ion in alkaline solution, and the latter is again oxidized to the former by air when it is bubbled through the solution soon after the reduction. But if the reduced colourless solution is allowed to stand, the oxidizability of bivalent manganese diminishes with the lapse of time. It seems that manganese(II) triethanol-amne complex changes gradually to a new complex coordinating with cyanide ion, which is incapable of being oxidized to manganese (III) triethanolamine complex.
Provided that the concentration of cyanide ion is less than ca. 0.02 M, the reduction of manganese in this case proceeds very slowly and the effect is negligible for the determinaiion of manganese.