Polarographic behaviour of aluminium and beryllium in the presence of oxamide and rubeanic acid

Abstract

The polarographic behaviour of aluminum and beryllium in the presence of oxamide and rubeanic acid was examined. Potassium chloride, lithium chloride and tetraethylammonium iodide were used as supporting electrolytes. At pH 4.4–9, oxamide produced a well defined wave whose half-wave potential for concentrations of 0.08–1.0 m M was within the range −1.66 to −1.70 V vs. SCE and which showed a linear relation between concentration and diffusion current. At pH values below 4.4, part of the oxamide wave was shifted towards more positive values. The height of this wave, with a half-wave potential of −1.40 to −1.50 V vs . SCE, was linearly proportional to the concentration of hydrogen ions. On the addition of aluminium ions to solutions of oxamide at pH 4.4–5.0 a portion of the oxamide wave was shifted towards more positive values. The height of the wave so produced was linearly proportional to the concentration of trivalent aluminium. For concentrations of 0.1–1.5 m M Al 3+ the half-wave potential was between −1.45 and −1.48 V vs . SCE. A similar phenomenon occurred on the addition of beryllium ions to a solution of oxamide at pH 4.4–5.3. The wave-height was linearly proportional to the concentration of bivalent beryllium. The halfwave potential for 0.2–1.4 m M Be 2+ ranged from −1.54 to −1.58 V vs . SCE. In the presence of rubeanic acid, trivalent aluminium produced at 0.5–6.0 m M , a wave of E 1/2 −0.68 V vs . SCE. Beryllium gave a flat and poorly defined polarographic wave in the presence of rubeanic acid.