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Redox substoichiometry in the isotope dilution analysis of antimony was studied. As the substoichiometric reaction the oxidation of trivalent antimony to pentavalent with potassium permanganate was used, followed by the BPHA extraction of trivalent antimony. The redox substoichiometry was applied to the determination of antimony content in 124Sb obtained from JAERI. The content determined was 0.481±0.02 μg, which agreed with the certified value.

We have proposed the determination of the kinetic parameters of the electrode reaction by means of convective voltammetry. At the pushed-out mercury-drop convection electrode (PM-DCE), the ratio of the current on a totally-irreversible wave to the limiting current was derived as follows:(Remark: Graphics omitted.)This equation was applied to the determination of the kinetic parameters for the electro-reduction of cupric ions in a 0.1 mperchloric acid solution containing 0.05% Triton X-100. It was found that the values of αnand k°the kinetic parameters are 0.59 and 4.2×10−9cm/sec respectively.

The convection electrode system was applied to the determination of the kinetic parameters of the electrode reaction. By analyzing the observed current-voltage curve, the parameters of a and k°were calculated; for the ferric-ferrous system in 0.1mperchloric acid, a and k°were found to be 0.63 and 7.6×10-3cm/sec respectively, while for the hexammine cobaltic-cobaltous system in 1mammonia-ammonium chloride, they were 0.65 and 4.5×10-6cm/sec respectively.

The investigation of the anodic-stripping voltammetry of cadmium or thallous ions in a 0.1 mpotassium nitrate solution was carried out by using the pushed-out mercury Drop Convection Electrode (cf.J. Suzuki and T. Ozaki, This Bulletin, 37, 230 (1964)). The metals were deposited on the mercury electrode by rotating the disk at 600—1200 rpm, and the stripping was performed by a linearly-varying potential method. The anodic-stripping peak current was proportional to the square roots of the rotating rate of the disk and of the voltage scanning rate, and to the bulk concentration of cadmium or thallous ions. Using the present stripping procedure, it was possible to determine thallous and cadmium ions at concentrations as low as 1×107mwith a mean error of about ±2%.

The cathodic stripping voltammetry of chloride ions in a potassium nitrate or a nitric acid solution was studied by using the Pushed-out Mercury Drop Convection Electrode (PMDCE) (J. Suzuki and T. Ozaki, This Bulletin, 37, 230 (1964)). The cathodic stripping peak current, ip, depended upon the rotating rate of the disk, ? (600—1000 r. p. m.); the rate of voltage scan, v(100—300 mV./min.); the pre-electrolysis time, t(~3 min.), and the bulk concentration of chloride ions, C. It was concluded that the corresponding cathodic peak current, ipcan be given by the equation:ip=kv?1/2Ct2/3where kis the constant. In a 0.1 mnitric acid solution, it was possible to determine the chloride ions in so dilute a solution as 3×105-mwith a good reproducibility.

A.C. polarography with the PMDCE has been investigated, using cadmium in 1 mhydrochloric acid.A satisfactory proportionality between the summit current and the concentration is obtained in the range from 1×10−4to 2×10−6m, and the summit current obtained with the PMDCE (in the presence of dissolved oxygen at the stirring rate of 600 r.p.m.) for the cadmium depolarizer is about thirty times as large as the corresponding diffusion current obtained with the DME.The a.c. polarogram obtained with the PMDCE shows a gradual decrease in the summit current as the stirring increases; this decrease is considered to be due to the quasiirreversibility at the electrode reaction because of the increase in the rate of mass transfer caused by the convection. The relation between the summit current and the stirring rate is exponential in the range from 600 to 1200 r.p.m.

The limiting currents with the PMDCE depend on the factors of both convection and diffusion. The PMDCE is easy to prepare and to manipulate, and it has an excellent sensitivity. It can be used even in a strongly alkaline or acidic medium and can be reused many times with good reproducibility. Therefore, various applications to analytical chemistry can be expected.