Ionic strength effects in the synergistic solvent extraction of Co2+

The extraction of Co²⁺ by a mixture of acetylacetone (acac) and pyridine (py) from an aqueous phase of varying ionic strengths has been investigated. The extraction studies were done at different temperatures in order to determine the effect of changes in the ionic strength on the free energy ΔG, enthalpy ΔH and entropy ΔS of the synergistic reaction.     

Study of the surface properties of titanium hydroxide using a radioactive tracer technique

The surface properties of titanium hydroxide precipitates, formed under different conditions were studied in the presence of carrier-free radioactive⁸⁹Sr. It was found that titanium with concentrations equivalent to 24 mg TiO₂/litre, was enough to remove by adsorption more than 95% of the carrier-free strontium activity from an alkaline solution (pH≈13) in less than 6 hrs, regardless of whether the precipitate was freshly prepared or aged for a few days. If the precipitate was formed in situ, at the above pH value, the percentage removal of the strontium activity from the solution was even greater, and this was attributed to an internal adsorption process. At a lower pH value (∼2.5), however, the adsorption of strontium activity by titanium hydroxide was very low (<5%), whether the precipitate was preformed or formed in situ. The increase in the adsorption ability of titanium hydroxide precipitate on going from low pH (2. 5) to higher values was attributed to the inversion of the charge of titanium hydroxide sols from cationic particles at pH 2. 5 to negatively-charged particles at pH>3. 5, these latter particles adsorbing any positive strontium ions in solution.     

Solvent extraction studies using phosphonic acid monoesters

The extraction of radioactive⁶⁰Co by ethyl hydrogen benzoyl phosphonate (HEBOP) has been investigated. Different parameters that may effect this extraction such as the change in pH and [HEBOP] were studied. Extraction was carried out in three organic solvents. In addition, the equilibrium constants were determined at different temperatures and the thermodynamic parameters for such extraction process were calculated.     

Studies on metallic azides

The stability constant for the formation of Pr(N₃)²⁺ has been measured by using solid cation-exchange resin (Dowex-50), and found to be 1.26±0.12 at 22±2 °C and μ=2.0M. Radioactive¹⁴³Pr was used as a tracer.     

Salt effects in the synergistic solvent extraction of Co2+

The extraction of Co²⁺ by mixtures of acetylacetone (acac) and either pyridine (Py), benzylamine (ba), triethylamine (tea) or tripyridylamine (tpa) bases in xylene solvent was investigated from an aqueous phase containing salts of LiCl, NaCl, KCl, RbCl and CsCl in concentrations varying up to 3M. The different hydration properties of the alkali metal cations is show to affect very slightly the synergistic solvent extraction of Co²⁺. This result, together with previously obtained thermodynamic data indicating the nonexistence of water molecules in the extracted synergistic species, may explain the fact that these salts have no effect on the extraction of Co(acac)₂ (N-base)₂.     

Thermodynamics of the extraction of europium(III) radiotracer by benzyl-phosphonic acid monoester

The extraction of Eu³⁺ from perchloric acid by ethyl hydrogen benzyl phosphonate (HEBP) dissolved in a series of organic diluents, has been studied at different temperatures. From the variation of the distribution ratio with temperature, the thermodynamic functions H, S and G have been determined. The meaning of the experimentally obtained thermodynamic quantities is discussed.     

A Characterization of Certain Families of Strong Parapolar Spaces

A broad class of strong parapolar spaces is characterized by the properties of having all symplecta of rank at least 3, having finite singular rank, and possessing a geometric property (WH) concerning 6-circuits which are embedded in so as to contain a distance-3 pair of antipodal points. The geometries in question belong to a class F of strong parapolar spaces which entered the scene as a class for which the existence of Veldkamp lines could be proved. The paper attempts to transcend the characterization theorem, by giving a natural context in which one might expect to encounter the basic hypothesis of the Cohen–Cooperstein characterization theorem – namely a gap in the spectrum of projective ranks of subspaces x S, where x is a point not in the symplecton S. The theorem of the previous paragraph is then seen simply as an application of the principles advanced in this one.     

Isotopic exchange between manganese hydroxide and manganese ions in aqueous solution

Heterogeneous isotopic exchange between manganese hydroxide and manganese ions in aqueous solutions tagged with radioactive⁵⁴Mn has been studied at different values of α, the ratio of the quantity of exchangeable ions in the solid phase to that in the liquid phase. The aging of the precipitate in its mother liquor prior to the exchange has a significant effect on both the extent and rate of the exchange reaction. A marked feature of great interest is the appearance of two aging-times, one at about 10² and the other at about 10⁴ min. The overall reaction appears to be of the consecutive type. In the case of a fresh precipitate, “complex-surface-exchange” and “self-diffusion” mechanisms are the most probable rate-determining steps in the initial and final stages of the reaction, respectively. “Complex-surface-exchange” is a new suggested mechanism. In the case of a well-aged precipitate, “surface-exchange” and ‘self-diffusion” mechanisms are the most probable-determining steps in the initial and final stages of the reaction, respectively.     

Heterogeneous exchange reactions of unstable simple systems

The analysis of less than 10⁻⁹ g of the isotope²⁰⁴Pb in lunar samples was carried out by an (n, 2n) activation using high energy (>8. 8 MeV) neutrons. A procedure of using the neutrons produced by bombardment of a specially designed Be sample holder with deuterons in a cyclotron was developed and compared to irradiation carried out in the core of a nuclear reactor, Radiochemical separations and X ray-γ ray coincidence counting techniques are necessary to achieve the required sensitivity. Although the flux of neutrons of sufficient energy from the cyclotron procedure is somewhat lower can be obtained in the best reactor irradiations, the high radioactivity due to other elements produced by the (n, γ) reactions in the reactor is eliminated. Radiochemical procedures for the analysis of Bi, Tl, Zn in the same samples are also described.     

Temperature effects on the synergistic solvent extraction of cobalt(II)

The extraction of Co²⁺ from a 0.1M ionic strength acetate buffer by acetylacetone, and a mixture of acetylacetone and pyridine or triethylamine was investigated at various temperatures. The enthalpy and entropy change data for the synergistic extraction support a model in which the Co²⁺ ion in the acetylacetonate complex expands its coordination number from four to six in order to accomodate the two N-base molecules. The steric hindrance caused by triethylamine is also reflected in the thermodynamic data.