Katsuo Takahashi

Effects of reactant and product adsorption in normal pulse polarography

Abstract Digital simulation is used to characterize the effects of the adsorption of reactants and products on the wave shapes and limiting currents of normal pulse polarograms. Pre-and post-waves induced by adsorption of reactants obeying non-linear isotherms are discussed. Analytical implications of the non-canonical relations between limiting currents and reactant concentrations are stressed.

Reactant adsorption in differential pulse polarography: Effects of adsorptive depletion of reactant, non-linear adsorption isotherms and uncompensated resistance

Abstract Digital simulation techniques are applied to the diagnosis of the ways in which the peak currents and wave shapes of differential pulse polarograms are affected by the adsorption of reactants or products. The changes in the polarograms introduced by the items mentioned in the title are examined and their magnitudes calculated and compared with experimental polarograms. Some implications of the results in analytical applications of differential pulse polarography are described.

Instrumental study of electrolytic conductance measurements using four-electrode cells

Summary A new apparatus was presented for the electrolytic conductance measurement by a four-electrode cell under controlled-current or controlled-potential conditions. The four-electrode cell method enables us to dry the whole cell without altering the cell constant and to use electrodes of any material unless they are attacked by the solution. The direct reading of solution resistance can be made with an accuracy of ±0.2%. When the resistance is measured by the null method and calibrated by the method of substitution, the accuracy is increased to better than 0.1% at frequencies less than 1500 Hz, provided that the resistance is less than several kiloohms. It was shown that the d.c. conductance can be determined with a reasonable accuracy by the same measuring apparatus. The present method can be applied to the absolute determination of electrolytic conductivity without calibrating the cell constant by using standard solutions of known conductivities. Because of these advantages, the present method is expected to be very useful in the conductance study of solutions where the conventional two-electrode methods fail to give reliable data.

Electrochemical reactions of dichlorobis(aryl isocyanide)platinum(II) complexes

Electrochemical reduction of cis-[PtCl2(RNC)2][(1a), R = 2,4-But2-6-Me6H2; (1c), R = 2,4,6-But3C6H2] produced [Pt2Cl2(RNC)4](2) or [Pt3(RNC)6](4), depending on the charge consumed and reduction potential. Potentiostatic reduction of [PtCl2(2,6-Me2C6H3NC)2](1b) gave [Hg{Pt3(2,6-Me2C6H3NC)6}2](3b)via a two-electron transfer process. [Pt2Cl2(RNC)4](2) was formed by the chemical reaction of cis-[Pt2Cl2(RNC)2] with zero-valent complexes (3) or (4) which were obtained by the above electrochemical process. The structure of compound (2) consists of two perpendicular PtCl(RNC)2 planes joined by a Pt–Pt bond; extended Huckel molecular orbital calculations on [Pt2Cl2(HNC)4] indicate that the perpendicular geometry is more stable than the planar one. Reaction of binuclear complexes (2) with isocyanide in the presence of [NH4][PF6] or NaClO4 gave [Pt2(RNC)6][X]2(8)(X = PF6 or ClO4). In the electronic spectra of the binuclear complexes (2) and (8) the absorption near 320 nm is assigned to a σ–σ* excitation.