Electrogeneration of gold(III) in halide media

Gold(III) was electrogenerated with high efficiency at constant current in halide media by oxidation of freshly electrodeposited gold on a platinum electrode. The electrolytes tested were 0.0005–1 M HCl, NaCl HBr, and NaBr. Potentiometric studies indicated that the tetrahaloaurate(III) complex was generated in each case with oxidation potentials ranging from 0.83 to 1.15 V. Arsenic(III) (20 μeq) was titrated potentiometrically in 0.1 M NaBr by using a gold indicating electrode; the efficiency was 99.90 ± 0.05%. Iron(II) was titrated in 0.01 M HCl to a biamperometric end-point with gold-plated platinum wire indicating electrodes polarized at 100 mV. Recoveries were 100.7± 1.8% (0.7 mg) and 100.4 ± 2.3% (0.4 mg). This new system allows titrations over a wide range of acidities and oxidation potentials.