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- Author or Editor: S. Chen x
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Abstract
Neutron activation analysis has been applied to the determination of ultra-trace amounts of arsenic based on the substoichiometric extraction of As(III) with thionalide. The arsenic content in high-purity trichlorosilane or silicon can be determined by the proposed method down to sub-ppb range with a very good reproducibility. Also, the data obtained were compared with results from atomic absorption spectrophotometry.
Abstract
Destructive and non-destructive methods have been used for the determination of microtraces of antimony in high-purity silicon powder. The destructive method was based on substoichiometric radioactivation analysis with solvent extraction using BPHA and cupferron as organic reagents. The antimony contents in high-purity silicon can be determined by the proposed method.
Abstract
Dibutyl-and monobutylphosphoric acid in acidic toluene medium were determined by ion chromatography. The procedure involved stripping with dilute sodium hydroxide solution and used carbon tetrachloride as diluent, then detection with a conductivity meter. The effect of flow rate, eluent strength and stripping solution, the effect of chloride and nitrate ion on DBP, the effect on DBP in sodium hydroxide solution, and the effect of organic aliphatic acids were discussed. The detection limits of 0.19 ppm and 0.14 ppm were found for DBP and MBP, respectively.
Abstract
A method is described for the determination of gallium and other trace elements such as Ce, Cr, Hf, Lu and Th in bauxite by the technique of neutron activation analysis using gold as internal standard. Isopropyl ether was used as organic extractant to extract radioactive gallium from the sample. This method yields very good accuracy with a relative error of ±3%.
Abstract
Some criterions in order thatl 1 embeds complementably inE Φ(μ) and inL Φ(μ) are given. It is also proved that every idealL inL Φ(μ) such thatI Φ(x/‖x‖Φ)=1 for anyxεL/{0} is contained inE Φ(μ).
Abstract
Radiobrominations of cetyl bromide with82Br in several organic media such as DMF, 18-crown-6, DMSO, pyridine and n-butanol were achieved and a comparison was made as to the labelling rates. The rate order was found as follows: DMF>18-crown-6>DMSO>pyridine } n-butanol which was attributed to increased anion /i.e., the nucleophilic bromide ion,82Br–/ solvation. Labelling in pyridine or alcohol was found to be too slow to meet practical needs. A suitable crown ether such as 18-crown-6 was found to be favourable for rapid radiobromination. However, it was discovered unexpectedly that dimethylformamide /DMF/ was superior to 18-crown-6. We therefore recommend DMF as an alternative reaction medium for fast radiobromination considering that this solvent is inexpensive and readily available.
Abstract
Fourteen new complexes with the general formula of Ln(Hmna)3·nH2O (n=2 for Ln=La-Ho and n=1 for Er-Lu, H2mna=2-mercaptonicotinic acid) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the prepared complexes revealed that carboxyl groups of the ligands coordinated with Ln(III) ions in bidentate chelating mode. Hydrated complexes lost water molecules during heating in one step and then the anhydrous complexes decomposed directly to oxides Ln2O3, CeO2, Pr6O11 and Tb4O7. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as ‘tripartite effect’. It suggested a certain amount of covalent character existed in the bond of Ln3+ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions.
Abstract
Five new complexes M(Hmna)2 [M=Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4) and Zn(II) (5), H2mna=2-mercaptonicotinic acid] have been synthesized and characterized by elemental analyses, IR spectra, thermogravimetric analyses. In addition, molar specific heat capacities and enthalpy changes of reactions were determined by a microcalorimeter at 298.15 K. All the complexes exhibited similar IR spectra, the sulfur and oxygen atoms from monoanionic Hmna− ligand coordinated to M2+ in a bidentate fashion. The thermal stability of M(Hmna)2 complexes varied in the sequence 1>2>3>4>5. The complexes were stable up to about 300°C and decomposed to oxides at higher temperatures. The molar specific heat capacities of the complexes were determined in the range between 106.452±0.399 and 145.920±0.423 J mol−1 K−1. The enthalpy changes of reactions, Δr H m θ, were determined from 18.28±0.05 to 52.59±0.07 kJ mol−1 for complexes 1–5, indicating that the thermodynamic stability of M(Hmna)2 increased in the sequence from Mn2+ to Zn2+.
Two Mn(II) chloride complexes containing guest molecules
Solvothermal syntheses, crystal structures and thermal decomposition
Abstract
Two phenanthroline-manganese inclusion complexes with [MnCl(H2O)(phen)2]+ core have been synthesized and characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric analyses. Uncoordinated 2-mercaptothiazole (tzdtH) and 2-mercaptobenzothiazole (bztzH) as guest molecules are included in the complexes with formulas [MnCl(H2O)(phen)2]Cl·tzdtH (1) and {[MnCl(H2O)(phen)2]Cl}2·bztzH (2). X-ray structural analyses for complexes revealed that the complex 1 is triclinic, space group P1 with a=9.724(1) Å, b=11.858(1) Å, c=12.644(2) Å; β=89.056(2)°; Z=2, D c=1.513 Mg m−3, F(000)=638 and the complex 2 is triclinic, space group P1 with a=9.861(1) Å, b=11.476(1) Å; c=12.908(3) Å; β=84.991(2)°; Z=1, D c=1.511 Mg m−3, F(000)=600. Two complexes exhibit high stability up to 650°C. The molar specific heat capacities for the two complexes 1 and 2 can be estimated as being 96.175±0.332 and 72.505±0.364 J mol−1 K−1 at 298.15 K by RD496-III microcalorimeter, respectively.
Abstract
A new complex, diaquadi(1,2,4-triazol-5-one)zinc(II) ion nitrate formulated as {[Zn(TO)2(H2O)2](NO3)2}n (1) (1,2,4-triazole-5-one, abbreviated as: TO) was synthesized and characterized by elemental analysis, X-ray single crystal diffraction, infrared spectrum (IR), differential scanning calorimetry (DSC), thermogravimetric analysis and differential thermogravimetric analysis (TG-DTG). The X-ray structure analysis reveals that the complex is orthorhombic with space group Pbca and unit-cell parameters a=6.9504(2) �; b=10.6473(3) �; c=17.8555(5) �. Based on the result of thermal analysis, the thermal decomposition process of the compound was derived. From measurement of the enthalpy of solution in water in 298.15 K, the standard molar enthalpy of solution of lignand TO and the complex were determined as 15.43�0.18 and 52.64�0.42 kJ mol−1, respectively. In addition, the standard molar enthalpy of formation of TO(aq) was calculated as −126.97�0.72 kJ mol−1.
