Investigations in platinum metal group electrochemistry: I some iridium (IV) — iridium (III) systems

Abstract

The ‘Norbide’, boron carbide, electrode has been shown to be exceptionally good in terms of its chemical inertness, rapid response and high hydrogen overvoltage. It has been applied especially in potentiometric and polarographic studies of the Ir(IV)-Ir(III) system in various media. By its means, supported by evidence from use of other cathodes, certain previous work has been confirmed and standard or formal redox potentials of the following systems have been determined: Ir(IV)-Ir(III)-ClO ⁻₄ (M HClO₄, 1·27 V; Ir (IV)-Ir(III)-SO ²⁻₄ (0·18M H₂SO₄), 1·08 V; Ir(IV)-Ir(III)-PO ³⁻₄ (0·3M H₃PO₄), provisionally 0·99 V; IrCl ²⁻₆ -IrCl ³⁻₆ (0·1M NaClO₄ or NaCl), 0·899 V; IrBr ²⁻₆ -IrBr ²⁻₆ (0·1M NaClO₄or NaBr), 0·838 V. The potentials fall in the expected sequence. The possibility of analytical application of the ‘Norbide’ and rotating platinum electrode has also been examined.