Polarography with Alternating Currents. III. A.C. Polarography of Copper, Bismuth. Antimony, and Tin with Special Reference to thePresence of Halogen Ions

Abstract

The A.C. polarography of copper, bismuth, antimony, and tin is discussed with special reference to the effect of the presence of halogen ions on the reversibility of the electrode reaction. While Cu⁺⁺, Bi⁺⁺⁺, and Sb⁺⁺⁺ ions are irreversibly reduced in perchloric acid as supporting electrolyte, the electrode process becomes reversible when small amounts of halogen ions are added. It is shown that this cannot be explained by assuming the formation of complex halogeno metal ions. Sn++ ions in perchloric acid are reversibly reduced, but only in the presence of a large excess of chloride ions, indicating a reduction of the stannous tetrachloro complex ion (SnCl₄^2-), as already observed by previous workers. A new polarographic cell design suitable for A.C. polarography (the "pool- condenser " saturated calomel electrode) is described in Appendix I.