XRF estimation of Cd,Hf, Hg,and Gd in uranium solution

A new curriculum in radiochemistry for undergraduate chemistry is described.     

Pyranopyrazoles. II. Synthesis and reactions of 1H,6H-pyrano[2,3-c]pyrazol-6-ones

Various 1H,6H-pyrano[2,3-c]pyrazol-6-ones (III-XXIII) were obtained from β-keto esters and 1H-pyrazol-5-ones or hydrazines. Nitrations, chlorinations and brominations of these pyranopyrazoles were also carried out giving the corresponding derivatives (XXIV-LXIV). The pyrone ring is the more reactive one in these reactions and the preferred position of attack is the 5-position. The substitution products are formed by the addition-elimination route.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazines

Summary.  A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-e][1,2,4]triazines

A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Isotope shift studies in the spectra of Gadolinium in UV region and term shifts of high even levels of Gd I

Isotope shift Δσ(¹⁵⁶Gd?¹⁶⁰Gd) is reported in 70 spectral lines of neutral gadolinium atom (Gd I) in the 3290- 3920 Å region providing isotope shift data in UV lines of Gd I spectrum for the first time. The measurements were carried out on a photoelectric recording Fabry-Perot Spectrometer using highly enriched isotopic samples of gadolinium. Term isotope shifts ΔT(¹⁵⁶Gd?¹⁶⁰Gd) have been evaluated for 48 high lying even parity energy levels of Gd I using this data; new ΔT values have been obtained for 24 levels. Electronic configurations 4f⁷5d6s6p, 4ff⁷5df²6p and 4f⁸5d6s assigned earlier to these even levels have been either confirmed or configuration mixing pointed out in some of these levels. Probable assignment of 4f⁸5d6s configuration to 8 even levels between 32 930 and 35 500 cm^-1 have been confirmed.     

Electrode Kinetics and Ternary Complex Formation of Cd2+‐Antibiotics‐Vitamin‐B5 System. A Polarographic Study

Cd²⁺ complexes with antibiotics viz. neomycin, chlortetracycline, oxytetracycline, tetracycline, penicillin‐V and penicillin‐G as primary ligands and vitamin‐B₅ as secondary ligand have been reported at pH = 7.30 ± 0.01 and μ = 1.0 M KNO₃ at 298 K by polarographic technique.¹ Cd²⁺ formed 1:1:1, 1:1:2, and 1:2:1 complexes with a stability constants trend of neomycin < chlortetracycline < oxytetracycline < tetracycline < penicillin‐V < penicillin‐G can be explained on the basis of the nature of ligands, bonding, and steric hindrance of these drugs. The nature of electrode processes were reversible and diffusion controlled. The values of stability constants showed that these drugs can be used to reduce the toxicity of Cd.     

Structural characterization of CeO(2)-ZrO(2)/TiO(2) and V(2)O(5)/CeO(2)-ZrO(2)/TiO(2) mixed oxide catalysts by XRD, Raman spectroscopy, HREM, and other techniques

Structural characteristics of CeO(2)-ZrO(2)/TiO(2) (CZ/T) and V(2)O(5)/CeO(2)-ZrO(2)/TiO(2) (V/CZ/T) mixed oxide catalysts have been investigated using X-ray diffraction (XRD), BET surface area, Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques. The CeO(2)-ZrO(2) (1:1 mole ratio) solid solution was deposited over a finely powdered TiO(2) support by a deposition precipitation method. A nominal 5 wt % V(2)O(5) was impregnated over the calcined (773 K) CZ/T mixed oxide carrier by a wet impregnation technique. The obtained CZ/T and V/CZ/T samples were further subjected to thermal treatments from 773 to 1073 K to understand the dispersion and temperature stability of these materials. In the case of CZ/T samples, the XRD results suggest the formation of different cubic and tetragonal Ce-Zr-oxide phases, Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), Ce(0.5)Zr(0.5)O(2), and Ce(0.16)Zr(0.84)O(2) in varying proportions depending on the treatment temperature. With increasing calcination temperature from 773 to 1073 K, the intensity of the lines pertaining to cubic Ce(0.6)Zr(0.4)O(2) and Ce(0.5)Zr(0.5)O(2) phases increased at the expense of cubic Ce(0.75)Zr(0.25)O(2), indicating more incorporation of zirconia into the ceria lattice. The TiO(2) was mainly in the anatase form whose crystallite size also increased with increasing treatment temperature. A better crystallization and more incorporation of zirconia into the ceria lattice was noted when CZ/T was impregnated with V(2)O(5). However, no crystalline V(2)O(5) could be seen from both XRD and RS measurements. In particular, a preferential formation of CeVO(4) compound and an intense tetragonal Ce(0.16)Zr(0.84)O(2) phase were noted beyond 873 K. The HREM results indicate, in the case of CZ/T samples, a well-dispersed Ce-Zr-oxide of the size approximately 5 nm over the bigger crystals ( approximately 40 nm) of TiO(2) when treated at 873 K. The exact structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic fluorite geometry and the TiO(2) is in anatase form. A better crystallization of Ce-Zr-oxides ( approximately 8 nm) over the surface of bigger crystals of TiO(2) was noted at 1073 K. A further enhancement in the crystallite size and zirconia-rich tetragonal phase was noted in the case of V/CZ/T samples. Further, the structure of CeVO(4) formed was also clearly identified in conformity with XRD and RS results.     

Characteristic absolute efficiency response curves of a high purity germanium detector in the energy range 50–1500 keV

The characteristic absolute efficiency response curves of a high purity germanium detector (HPGe) for different counting geometries have been established in the energy range 50–1500 keV by measuring the absolute efficiencies using both mono-energetic and multi-gamma emitting radionuclide point calibrated sources supplied by IAEA. Several fitting functions proposed in the literature were assessed for interpolation within the intermediate energy range of interest. The values of the function parameters have been determined by using the linear least square methods. The problems associated with the measurements of experimental efficiency data at small source–detector distances and the importance of the correlation matrix in the estimation of precise uncertainties have been shown. It was found that the inclusion of correlation matrices in the propagation of error formulae plays a significant role up to 450 keV gamma-ray energy and results in a drastic reduction of errors associated with the predicted efficiencies. The discrepancy at closer counting geometries in the absence of true gamma-gamma coincidence corrections is found to reach to about 30%.     

Regioselective synthesis of 1-aryl-3,4-substituted/annulated-5-(methylthio)pyrazoles and 1-aryl-3-(methylthio)-4,5-substituted/annulated pyrazoles

[reaction: see text] Highly efficient and regioselective synthesis of 1-aryl-3,4-substituted/annulated-5-(methylthio)pyrazoles and 1-aryl-3-(methylthio)-4,5-substituted/annulated pyrazoles has been reported via cyclocondensation of arylhydrazines with either alpha-oxoketene dithioacetals or beta-oxodithioesters.     

Surface stabilized nanosized Ce(x)Zr(1-x)O(2) solid solutions over SiO(2): characterization by XRD, Raman, and HREM techniques

Ce(x)Zr(1)(-)(x)O(2) solid solutions deposited over silica surface were investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques in order to understand the role of silica support and the temperature stability of these composite oxides. For the purpose of comparison, an unsupported Ce(x)Zr(1)(-)(x)O(2) was also synthesized and subjected to characterization by various techniques. The Ce(x)Zr(1)(-)(x)O(2)/SiO(2) (CZ/S) (1:1:2 mole ratio based on oxides) was synthesized by depositing Ce(x)Zr(1)(-)(x)O(2) solid solution over a colloidal SiO(2) support by a deposition precipitation method and unsupported Ce(x)Zr(1)(-)(x)O(2) (CZ) (1:1 mole ratio based on oxides) was prepared by a coprecipitation procedure, and the obtained catalysts were subjected to thermal treatments from 773 to 1073 K. The XRD measurements disclose the presence of cubic phases with the composition Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) in CZ samples, while CZ/S samples possess Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), and Ce(0.5)Zr(0.5)O(2) in different proportions. The crystallinity of these phases increased with increasing calcination temperature. The cell a parameter estimations indicate contraction of ceria lattice due to the incorporation of zirconium cations into the CeO(2) unit cell. Raman measurements indicate the presence of oxygen vacancies, lattice defects, and displacement of oxygen ions from their normal lattice positions in both the series of samples. The HREM results reveal, in the case of CZ/S samples, a well-dispersed nanosized Ce-Zr-oxides over the surface of amorphous SiO(2). The structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic geometry and exhibit high thermal stability. Oxygen storage capacity measurements by a thermogravimetric method reveal a substantial enhancement in the oxygen vacancy concentration of CZ/S sample over the unsupported CZ sample.