[in Japanese]

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Application of solvent extraction to the polarographic method of analysis is reviewed. In the polarographic method of analysis, in general, the interference of other elements which do not concern to the analysis is avoided in the way of selecting suitable electrolytes, appling .A.C. polarographic method and so on. There are, however, a few cases in which these procedures are not enough to get fine steps in waves. In such cases chemical seperation method must be applied. For the chemical separation method, the solvent extraction is a good one, especially of its high selectivity and its quickness. And combining this solvent extraction and the polarographic method in suitable ways, the extent of the polarographic method of analysis becomes much wider. Solvent extraction may be classified into chetate-and ion association-extraction. Tne former is used mainly for the separation and condensation procedure of elements which are to be determined, for the amount of metal extracted by this method is limited to low degree. The typical solvents for it are dithizone, cupferron and so on, which can be easily decomposed. On the contrary, in the latter, ion association system, a large amount of metal can be extracted, so that it can be applied not only to condensation of trace components but also to removal of principal components, thus it has a large extent of application. For instance, iron is separated and removed away from hydrochloric acid solution by ether extraction, while, in order to determine impurities in indium metal, indium is extracted from hydrobromic acid solution and removed out of the system. For other examples, to determine zinc in cadmium and tin in lead cadmium and zinc are extracted from thiocyanic acid solutions. Recently, amines having hlgn molecular weignn-a liquid anion cxchanger-are marked as a new type of extracting solvents. Extraction procedure with them will be utilized broadly in the case of determination of zinc in copper and in uranium, indium in cadmium and so on. As being applied to the determination of uranium, it seems a very interesting method to determine metal quantities in non-aqueous solution by polarograph. The procedures are as follows; metals are extracted to organic phase and the solution containing metals is diluted with other organic solvent of high polarity. And then, the metals are determined with the polarographic method in this diluted non-aqueous medium. (translated by S. Shibabe)

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The bond-types of the complexes are reviewed in relation with their nature in solution. The complexes are classified into two groups. One is the complexes of ionic bond and the other the complexes of covalent one (the penetrating complexes). About these two types of the complexes are referred to the following subjects. (1) The difference of the stabilities between them was emphasized and explained neatly from a view-point of the ligand field theory and of the hybridization orbital method. (2) The absorption spectra of the six-coordinated dG complexes (Oh) were described simply, with regards to the bonding in the complexes. (3) The two mechanisms of the electrode reactions were tentatively proposed for the ionic and the covalent complexes. Namely, the dropping mercury electrode can be regarded as a kind of donor (the ligand), of which coordinating ability becomes stronger the applied potential increases gradually. On this consideration, the electrode process for the ionic complexes is considered to take place through S_N1 reaction and the process for the covalent complexes proceeds through S_N2 reaction, respectively. As an example of the former, the mechanism for the electrode processes of amminenickel(ll) system is given schematically (Fig. 5). The mechanism of the latter case is considered as being most rprobable for the polarographic reduction of dicyano-bis-ethylenediamine cobalt (lll) ion, judging from the thermodynamic data of the electrode reaction (Fig.7). The mechanism of S_N2 reaction for the covalent complexes is generally supported by the facts that most penetrating complexes are not suffered from any change of the structure through net electrode reaction and the value of activation energy is not so large, compared with that of a bond energy. For the mixed liganded complexes the choice of the two mechanisms (S_N1 or S_N2) depends upon the weakness of the bond in its coordination sphere, since the weakest bond is naturally expected to be attacked with “a donor atom of mercury”.

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[in Japanese]

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It is well known that the catalytic wave of protein discovered by Brdicka' shows a double wave in the solution of ammoniacal ammonium chloride containing either divalent or trivalent cobalt, and in general, the waves found with a trivalent cobalt solution are larger than those found with a divalent cobalt solution at the same total cobalt concentra tion. Brdicka2), in the series of his studies on the catalytic hydrogen wave, described that the wave was quite different in character when the ammoniacal solution contained divalent or trivalent cobalt. In order to learn more of the nature of the catalytic wave, a series of amino acids was tested, and he found that only cystine or cysteine showed a effect similar to protein in ammoniacal cobaltous solution, and that each of these compounds gave rise to a wave which was in the same position as the second wave of protein. The appearance of catalytic wave by cystine in the cobaltic solution was not described by him, and the difference of the catalytic wave in ammoniacal solution containing divalent or trivalent cobalt has not been known up to now.
In 1954, Kalous and Ji.rsa discovered that during the polarographic investigation of cystine, the catalytic wave appeared even in the presence of trivalent cobalt in a solution of relatively high concentration, i.e., about 10^-3M. Recently, he reported4) a complicated electrode reaction of influence of trivalent cobalt on the reduction of cystine and presented an explanation for the mechanism of the catalytic wave by using Kalousek commutatorn.
In the present study, the catalytic wave of cystine with trivalent cobalt has been in vestigated by D.C. and A.C. polarograph to learn more of the electrode reactions. The parameters studied with respect to the effect on the catalytic wave were the concentration of cystine and cobalt and pressure of the dropping mercury electrode. A.C. polarographic waves showed the reduction waves corresponding to various D.C. polarographic waves given by cystine in the solution of ammoniacal trivalent cobalt. The relation between the reduction process of prewave of cystine (at -0.58 V.) and divalent cobalt at the surface of mercury produced by the reduction of trivalent cobalt, was investigated, and an explana tion for the mechanism of the catalytic wave was presented.

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It must be naturally considered that the nature of the catalytic hydrogen wave may depend on the structure of complexant forming with cobalt and some active groups in catalyst. It is probable that the self hydryl or disulfide group has a stronger tendency to react with cobalt than the amino group or the carboxyl group . The important role of sulf hydryl group was elucidated skilfully by Ilata. It is a well known fact that most compounds containing sulfhydryl or disulfide group and amino group and/or carboxyl group give the catalytic erect in cobaltous or cobaltic solution2).
Shinagawa et al.3 studied on the possibility of the Bis-cysteinate diaquocobaltate(III)4) as a catalytically active complex. The complex compound was considered to form by co ordination of nitrogen in amino group and sulfur atom in sulfhydryl group to trivalent cobalt.
Although several amino acids without sulfhydryl group have also been found to give catalytic effect in cobaltous or nickelous solution, these waves have quite different patterns from those of cysteine or cystine.
In this study, in order to learn more of the relation between the role of active group in the compound and the catalytic effect, L-cystine (-NH₂ -S-S-, and -COOH, i.e., three active groups), N, N'-diacetyl-L-cystine (-NHCOCH₃, -S-S- and -COOH, i.e., defect of -NH₂) and L-cystine-diethylester (-NH₂, -S-S- and -COOC₂H₅, i.e., defect of -COON) were selected and studied in both divalent and trivalent cobalt solution. Cystine-diethylester containing two amino and a disulfide group gave a catalytic wave in both divalent and trivalent cobalt solution, but no catalytic wave was seen with diacetyl-L-cystine containing two carboxyl and a disulfide group. As for the catalytic hydrogen wave of cystine, it was found that amino group played an important role as well as sulf hydryl or disulfide group.

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