[en] Polyurethane foam (polyether based) has been found to efficiently extract rhodium from hydrochloric acid solutions containing stannous chloride. The amount of rhodium extracted is significantly influenced by inter alia temperature, acid concentration, the Sn(II):Rh mol ratio and the presence of alkali metal cations. The extraction efficiency is promoted by increased acid concentration and high Sn(II):Rh ratios. The presence of K⁺ inhibits the extraction or rhodium, while the effect of Li⁺ and Na⁺ is small. A series of model urethane compounds (diurethane podands and linear polyurethanes) have been synthesized and characterized. These model compounds allowed the direct determination of the extracted trichlorostannato-rhodium complex anions by ¹¹⁹Sn nmr spectroscopy. The ¹¹⁹Sn nmr study showed the formation of a new rhodium-hydrido complex formulated to be [RhH(SnCl₃)₄Cl]^3-. In the presence of low tin(II) concentrations (Sn(II):Rh = 4:1), [Rh(SnCl₃)₃Cl₃]^3- is predominantly extracted by the foam phase. Analysis of the acid-decomposed polyurethane foam phase by atomic absorption spectroscopy and of the model urethane compound phase by ⁷Li nmr spectroscopy, confirmed the extraction of alkali metal cations from aqueous solutions containing alkali metal salts. It is indicated that the polyether chains of polyurethane foam play a major role in the extraction process, and that the flexibility of the chains influences the efficiency of polyurethane foam as an extractant. The creation of cationic sites within the foam matrix, which facilitate the extraction of the rhodium-tin complex anions, is postulated to occur by protonation of the donor oxygen atoms as well as by chelation of cations such as H₃O⁺, Li⁺, Na⁺ and K⁺ by the polyether chains. A working model for the extraction of the trichlorostannato-rhodium complexes by polyurethane foam is proposed. 79 figs., 51 tabs., 272 refs

[en] For some time now at Liverpool the reorientation effect in Coulomb excitation has been used to measure the static electric quadrupole moments of the first excited 2⁺ states in even-even nuclei in the Z=50 region. This work was prompted by the discovery of a nonzero moment of the first 2⁺ state of ¹¹⁴Cd and the consequent need to determine any systematic variation of quadrupole moment among neighbouring nuclei. Although the ¹¹⁴Cd result was in direct conflict with the harmonic vibrational model, vibrational motion is still in mind in describing nuclei in this region. They are near to the major shell closure for protons at Z=50 and have neutron numbers ranging across the middle of the 50< N<82 shell. Thus they are good condidates for the semimicroscopic, particle-vibrator coupling model in which they are seen as having a few extra core protons (or proton holes) coupled to a harmonic vibrational core. The results are discussed in the context of this model. All the reported quadrupole moment measurements (and not just the Liverpool results) on the isotopes Mo, Ru, Pd, Cd, Sn and Te are shown. (Auth.)

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[en] We report Moessbauer data between 1.3 K and 300 K, with applied fields of up to 10 T at 4.2 K of (NH₄)₂FeCl₅.H₂O. We found no evidence of a reported structural phase change just above T_N(∝7.3 K), nor did we see any spin reorientation just below T_N. The V_zz axis was found to be in the ac plane at ∝47deg to the a axis and the spins, below T_N, were found to be approximately parallel to the a axis. The spin reorientation in applied field occured gradually between 0 T and 5 T; this and previously reported susceptibility data have led to the hypothesis that (NH₄)₂FeCl₅.H₂O is a weak ferromagnet. (orig.)

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[en] Quadrupole moments measured by Coulomb excitation in the Z = 50 region, including previously unpublished measurements for ¹⁰⁰Mo and ¹¹⁶Cd, are summarized and compared with the magnitudes given by an approximate relation derived from collective model sum rules. (author)

[en] Single crystals of the mixed rare-earth orthoferrite Dy_1-xHo_xFeO₃ (x=0.25, 0.5, and 0.75) have been studied by Mossbauer spectroscopy in the 1.3-298 K temperature range. Several temperature-induced Fe³⁺ spin reorientation transitions have been observed. On cooling, a locally discontinuous reorientation from the a to the b orthorhombic axis took place near 40 K followed by a continuous reorientation from the b to the c axis. The onset temperature of the latter transition depends linearly on Ho concentration x. An x-T phase diagram of Dy_1-xHo_xFeO₃ is proposed which extrapolates well to the results of previous studies of pure HoFeO₃ and pure DyFeO₃. The continuous Fe³⁺ spin reorientation in the bc plane showed the hyperfine interactions of the ⁵⁷Fe nuclei to split into two branches. This branching is associated with different Fe unit cell positions. The temperature variation of the difference in magnetic hyperfine fields agrees well with a previous calculation of a similar effect in NMR. We also observed a new, very sharp Fe³⁺ spin reorientation from the c to the b orthorhombic axis upon cooling a Dy_1-xHo_xFeO₃ single-crystal absorber between 3 K and 2.3 R. We suggest that this transition is driven by ordering of the rare-earth spins and a microscopic mechanism is proposed. (author)