Tadatsugu Yoshikuni

Computer-assisted measurement of ion-diffusion coefficients by use of the cottrell equation

Abstract A computer-assisted technique based on application of the Cottrell equation is examined for the measurement of ion-diffusion coefficients. It is particularly useful for the investigation of unstable species because of the simple and rapid processing of data. Diffusion coefficients of chromium(III) and cobalt(III) complex ions are given.

Computer-aided measurement of kinetic parameters of electrode reactions of cobalt(III)—ammine complexes at mercury electrodes

A computer-aided technique based on Tast polarography is examined for the determination of kinetic parameters of electrode reactions. It is particularly useful for the investigation of unstable species because of the simple and rapid processing of data. Kinetic parameters of cobalt(III)—ammine complexes at mercury electrodes are given for [Co(NH3)6]Cl3, [Co(H2O)(NH3)5](ClO4)3, [Co(NO3)(NH3)5](NO3)2 [CoF(NH3)5](Cl04)2, [Co(C03)(NH3)5] NO3 ,cis-[Co(H2O)2(NH3)4] (Cl04)3 [Co(CO3)(NH3)4] NO3 · 0.5H20, [Co(ox)(NH3)4]Cl · H20, and NH4[Co(ox)2(NH3)2] · H2O, which are obtained in solutions containing 0.1 M acetate buffer and 0.005% gelatin at 25°C.

ECE mechanism as a tool for the investigation of unstable metal complexes: Part I. Electrochemical reduction of trans-[CoBr2(N)4]+-type complexes on the mercury electrode

Abstract A polarographic investigation of trans -[CoBr 2 (N) 4 ] + -type complexe where (N) 4 represents (NH 3 ) 4 , (ethylenediamine) 2 and (propylenediamine) 2 , has been carried out in acetate buffer solutions. These complexes gave two polarographic waves; the first wave corresponds to the reduction of Co(III) to Co(II) and the second to the reduction of Co(II) to Co(0). The relation between current and time of the first wave in a positive potential is dependent on the dissolution wave due to bromide ions produced by acid hydrolysis and parallel ECE mechanism. Overall reaction is as follows: at the electrode surface, [Co(III)Br 2 (N) 4 ] + + e - →[Co(II)Br 2 (N) 4 ] [Co(II)Br 2 (N) 4 ]+6H 2 O→[Co(II)(H 2 O 6 ] 2+ +2Br - +(N) 4 2Br - +2Hg→Hg 2 Br 2 +2 e and in the solution, [Co(III)Br 2 (N) 4 ] + +2H 2 O→[Co(III)(H 2 O 2 (N) 4 ] 3+ +2Br - The effects of the acid hydrolysis of a tervalent cobalt complex on the current—potential curve were simulated.

Kinetic parameters of the electrode reaction of chloropenta-amminecobalt(III) ions at a gold electrode

The cathodic reduction of chloropenta-amminecobalt(III) ions at active gold electrodes has been studied in 0.1 M HClO4 + 0.1 M NaClO4 by means of the potentiostatic method. Chloropentaamminecobalt(III) ions gave one irreversible reduction wave in the double layer potential region of gold electrodes. The kinetic parameters of the electrode reaction were measured at 5, 15, 25, 35 and 45°C, and the activation energy was calculated to be 19 kcal mol−1 for the electron transfer process and 4.5 kcal mol−1 for the diffusion process.