Tsai‐Teh Lai

POLAROGRAPHY OF URANYL-IMINODIACETATE COMPLEX.

Abstract The reduction of uranyl ion in iminodiacetate solution at dropping mercury electrode was studied in detail. The reversibility held at pH 1·80 to 11·00 and ligand concentration 0·14 M to 0·80 M. The pH values at the two breaking points in E 1 2 vs. pH plots were in excellent agreement with pK2 and pK2 of iminodiacetic acid. At pH pK1, the complex species of UO2(OH)A2−3 was formed. The uranium (V)-iminodiacetate complexes were proved to be stable toward disproportionation, and to undergo polymerization at high pH value. The pK value of UO2(HA)2 complex was found to be 3·92 ± 0·01.

Polarography and zone electrophoresis of uranyl-β-alanine complexes

Abstract The uranyl-β-alanine complex has been studied by polarography and zone electrophoresis over the pH range 0·7-5·4 and the ligand concentration range 0·203-0·812 M. The concentration of dipolar β-alanine ion for complex formation with uranyl ion at minimum pH value was calculated to be 4·5 times to the metal concentration. The concentration of hydroxyl ion for the complex beginning to attach to hydroxyl ligand was a linear function of the concentration of dipolar β-alanine ion. The complex species and electrode reactions were given.

Polarographic behaviour and determination of kinetic parameters for the electrode reaction of uranyl-pamoate complex in dimethyl sulfoxide

Abstract Uranyl-pamoate complex in dimethyl sulfoxide solution gives two reduction waves at pH 4·0–5·0 and pH 5·8–8·5, respectively. The first wave is the reduction of UO2(Dm)5Pm species when [DMSO] ≤ 60 vol.%, however it was proved to be the simultaneous reduction of the two species UO2(Dm)6+2 and UO2(Dm)5Pm when [DMSO] > 70 vol.%. The second wave is quasi-reversible, corresponding to the reduction of UO2(OH)(Dm)4Pm− species. The electron transfer coefficients, rate constants of electro-reduction and electro-oxidation, and polarographic overpotentials were determined. The hydrolysis constants of uranyl ion in dimethyl sulfoxide concentrations 50–70 vol.% at pH 4·0–4·8 were determined.

Polarography of uranyl-semicarbazide hydrochloride complexes

Abstract The complex formation of uranyl ion with semicarbazide hydrochloride has been studied polarographically. The concentration dissociation constant of semicarbazidonium ion, 2·0 × 10−4, for ionic strength 0·60–0·80, obtained from potentiometric titration is in excellent agreement with the polarographically determined value. The complex is proved to involve one chloride as the complexing species. This behaviour is distinctly different from the previous report which has shown that two chlorides existed as simple anions.

KINETIC STUDIES OF THE ELECTRODE AND DISSOCIATION REACTIONS OF URANYL--DTPA COMPLEXES BY POLAROGRAPHIC METHOD.

Abstract The uranium-DTPA chelate gives a two-step irreversible reduction wave when the concentration of surface-active substance, Triton X-100, is greater than 0·003%, due to the adsorption of surface-active substance on the mercury electrode. The limiting current of the first wave is controlled partially by the rate of electrode reaction. The electrode reaction of the second wave is a rate-determining step corresponding to the dissociation of the uranyl-DTPA chelate. The rate constants of the electrode and dissociation reactions were determined. The limiting current and the rate constants are a function of the concentration of Triton X-100. The dissociation rate constants are pH dependence and correlated by the equation k 1 − = −3·47 log [H + ] −13·2.