Search

Conductometric and spectrophotometric (covering the visible, UV, and IR ranges) studies as well as microanalyses of uranyl complexes with tetracycline revealed the existence of the 1:1 complex species. The mean stability constant of the 1:1 complex, as determined spectrophotometrically, amounted to 1.2 × 105. This finding permits the use of the procedure for the microdetermination of tetracycline using UO2+2ion or vice versa.

The formation constants of pyridin-2-ylthioureas with 3 d transition metals (Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ and Zn 2+ ) have been determined in 75% ethanol-water medium. The effect of metal ion, ionic radius, electronegativity and nature of ligand on the formation constants are discussed. The formation constants of the complexes with 3 d transition metals follow the order: Mn 2+ 2+ 2+ 2+ > Zn 2+ . Complexes of Cu 2+ , Ni 2+ and Co 2+ with pyridine-2-ylthioureas have been isolated and characterized by conductance, IR and magnetic measurements. The ligands form bis-complexes of octahedral arrangement and of general formula ML 2 , where L is the uninegatively charged tridentate ligand (ONS donor set) and M is Co or Ni. The ligands also form bis-complexes with Cu 2+ , characterized by anomalously low magnetic moments (0.16–0.22 B.M.), which are suggestive of CuCu interaction in binuclear, ligand-bridged structures.

The Sn/electrodeposited SnS electrode system was anodically polarised using rapid galvanostatic rectangular pulses. Values for the layer impedance have been calculated from the observed resistance overpotential; dependence of the specific impedance on the layer thickness reveals the effect of structural changes in the semiconducting properties of the layer. It has been argued, based on the activation overpotential-current density (c.d.) relations, that the electrode kinetics are determined by reaction at the layer/solution interface, at relatively low c.d. At higher c.d., the rate-determining step is more likely the diffusion of Sn2+ through the layer, contributing appreciably higher over-potentials. Approximate values for the rate constants, k and k′, corresponding to the specific reactions determining the electrode kinetics are calculated from the corresponding kinetic parameters.

Summary The conductance of ∼5×10−2-5×10−5 M uranyl acetate solutions in water and water-dioxane mixtures has been measured at 25°C. The dissociation constants K1 for the ion-pair, and K3 for the triple-ion dissociation of uranyl acetate are evaluated in each solvent up to 70 wt.% dioxane, using Λ0-values calculated after the methods of Fuoss-Kraus-Bray. Using these K1-and K3-values, the interionic charge distances for ion-pair, a1, and the triple-ion, a3, are estimated. These measurements indicate that uranyl acetate behaves in water and in water-dioxane mixtures as a weak electrolyte, as previously predicted for other uranyl salts. In the mixed solvent of 82 wt.% dioxane (D=10) the conductance of solutions Comparison of the conductance and spectrophotometric and pH-measurements with those obtained for other uranyl salts corroborates the view that the U3O82+ ionic species represents the main hydrolysis product.

Summary Conductometric and spectrophotometric studies on the complexes of uranyl ions with 5-norvisnagin, 1-hydroxy-9-xanthenone and 8-hydroxyquinoline have been carried out in pure dioxane and dioxane-water mixture, D =30. In every case, conductometric titration shows breaks corresponding to the formation of more than one type of complex. For both 5-norvisnagin and 8-quinolinol breaks correspond to the ratios uranyl: ligand of 1:1, 1:2 and 1:4; with 1-hydroxy-9-xanthenone, the compositions 1:1 and 1:3 are identified. Spectrophotometric studies covering the visible and u.v. range indicate considerable stability of the 1:3 complex with 1-hydroxy-9-xanthenone (applying the molar ratio method). The continuous variation method establishes the existence of 1:2 uranyl complexes with both 5-norvisnagin and 8-quinolinol. Complexes precipitated from the above media at the stable compositions indicated, are spectrophotometrically scanned in the region 600–200 nm. Characteristic peaks for these complexes are observed at the same wave lengths as shown in solution. Microanalysis for carbon and uranium in the complexes separated are in fairly good agreement with the compositions proposed, especially for 5-norvisnagin and 8-hydroxyquinoline where pure crystals of the complexes could be prepared.