Search

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.