Fundamentals of coulostatic analysis which is a new electroanalytical method, are reviewed with 7referencess. The principle of this method is as follows ; a known quantity of electricity is supplied to a working electrode, which is adjusted at the poten-tial at which no faradaic current flows, by discharging a capacitor across the cell. The capacitor is charged at such a voltage that the electricity in the capacitor is enough to bring the electrode potential to the range where the faradaic current is appreciable. At open circuit, the electricity required for the faradic process is not supplied from the outer circuit but from the double layer cpacity, and the electrode potential tends to shift to an original value before charging. The shift of the potential ΔE depends on the double layer capacity and the concentration of the analyzed substance, varying linearly with t^1/2.Thus the concentration of the analyzed substances is determined from the slope of ΔE versus t^1/2 plot. This method is most useful in the range of 10^-5-10^-7 M. The range, however, can be extended up to 10^-310^-4 M by inserting a parallel capacitor with the cell and down to 10^-8 M by combining with anodic stripping. If the double layer capacity is independent of the electrode potential, one deduces equations (2)-(5) for potential-time relationship during the decay under the conditions in Table 1. Instruments for determination of the decay curve are shown in Figures 1, 2 and 4. As a working electrode a hanging mercury drop electrode, a mercury pool electrode, cylindrical platinum electrode and a rotating disk electrode could be used, in which a hanging mercury drop electrode is most preferable and used though this experiment. Experimental results are shown for the redution of zinc ion with hanging mercury drop electrode in Figures 5 and 6 and Table 2. ΔE versus t^1/2 plots are nearly straight and experimental ΔE's after correction for the blank are in good agreement with theoretical values. The calculated values, except for lower concentration, are slightly larger than the experimental values, which may be at-tributed to the variation of the double layer capacity. Experimental results are given for the reduction of iodate ion in Table 3, and the same tendency as for zinc ion is ob-served. Lowereing of the sensitivity by a parallel capacitor with the cell (Fig. 7) and the influence of cell resistance are also discussed. Up to 300.000 ohms of cell resistance, no effect is detected on the potential decay curves. Analysis of a mixture is carried out. The result for the mixture of zinc and cadmium ions are given in Table 4. The limitation on the permissible ratio of concentrations is similar to that in classical polarography. The concentration of a substance should not exceed 10 times that of the other substance. A direct reading instrument is described (Fig. 2), in which the cell voltage during the potential decay is sampled, stored in cacitors and read with a vacume tube electrometer. The results for the reduction of zinc ion are shown in Table 5 and Figure 8. Potential-time curves are recorded with a pen-and ink recorder and an electrometer instead of an oscilloscope. The results obtained with a Sargent pen-and-ink recorder are more repro-ducible than those with an oscilloscope (Table 6). Coulostatic analysis is combined with anodic stripping with a mercury electrode. The plating from stirred and unstirred solu-tions is discussed. Experimental results are given for zinc determination, in which the plating is carried out from stirred solutions (Figs. 9, 10 and 11). The methods of differ-ential coulostatic analysis and coulostatic titration are described.

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In D.C. polarographic studies on the electrode processes of riboflavin since Brdicka1 5), it has been considered that only leucoform (reductant) of riboflavin is adsorbed on the mercury electrode. But recently Senda et a16). and Breyer et a17). have presented the evidence of the adsorption of both riboflavin (oxidant) and leucoform on the electrode in A.C, polarographic studies. Lorenz8) proposed theoretical equations on the adsorption processes in electrolysis at controlled current density, which are applicable to any type of adsorptions accompanied by electrolysis of the adsorbed species.
The author reports experimental results in chronopotentiometric study on the adsorption wave of FMN mainly in the concentration range of 10^-6-10^-5 mol/l in which the surface of mercury electrode is considered to be unsaturated with adsorbed FMN molecules according to the knowledge in polarography.
A noticiable feature of the results in the present study is that constancy of i₀τ values (i₀, current density; τ, transition time) was observed in a given concentration range and at current density chosen in a certain range and consequently the value of i₀τ/nF corresponds to the density of adsorbed species on the electrode surface at potential before applying current pulse.

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