A computational study of SbnF5n (n = 1-4): Implications for the fluoride ion affinity of nSbF5

This contributions shows with a series of ab initio MP2 and DFT (BP86 and B3-LYP) computations with large basis sets up to cc-pVQZ quality that the literature value of the standard enthalpy of depolymerization of Sb₄F_20(g) to give SbF_5(g) (+18.5 kJ mol⁻¹) [J. Fawcett, J.H. Holloway, R.D. Peacock, D.R. Russell, J. Fluorine Chem. 20 (1982) 9] is by about 50 kJ mol⁻¹ in error and that the correct value of (Sb₄F_20(g)) is +68 ± 10 kJ mol⁻¹. We assign , , and values for Sb_nF_5n with n = 2-4 and compare the results to available experimental gas phase data. Especially the MP2/TZVPP values obtained in an indirect procedure that rely on isodesmic reactions or the highly accurate compound methods G2 and CBS-Q are in excellent agreement with the experimental data, and reproduce also the fine experimental details at temperatures of 423 and 498 K. With these data and the additional calculation of [Sb_nF_5n+1]⁻ (n = 1-4), we then assessed the fluoride ion affinities (FIAs) of Sb_nF_5n(g), nSbF_5(g), nSbF_5(l) and the standard enthalpies of formation of Sb_nF_5n(g) and [Sb_nF_5n+1]⁻_(g): FIA(Sb_nF_5n(g)) = 514 (n = 1), 559 (n = 2), 572 (n = 3) and 580 (n = 4) kJ mol⁻¹; FIA(nSbF_5(g)) = 667 (n = 2), 767 (n = 3) and 855 (n = 4) kJ mol⁻¹; FIA(nSbF_5(l)) = 434 (n = 1), 506 (n = 2), 528 (n = 3) and 534 (n = 4) kJ mol⁻¹. Error bars are approximately ±10 kJ mol⁻¹. Also the related Gibbs energies were derived. Δ_fH°([Sb_nF_5n+1]⁻_(g)) = −2064 ± 18 (n = 1), −3516 ± 25 (n = 2), −4919 ± 31 (n = 3) and −6305 ± 36 (n = 4) kJ mol⁻¹.     

Thermal expansion and cation disorder in Bi2InNbO7

The structure of the pyrochlore-type oxide Bi₂InNbO₇ has been investigated between room temperature and 700 °C using electron and synchrotron X-ray powder diffraction and at room temperature and 10 K using neutron diffraction methods. Bi₂InNbO₇ exhibits an A₂B₂O₇ cubic pyrochlore-type average structure at all temperatures that is characterized by an apparently random mixing of the In³⁺ and Nb⁵⁺ cations on the octahedral B sites. The Bi cations on the eight-coordinate pyrochlore A sites are displacively disordered, presumably as a consequence of their lone pair electron configuration. Heating the sample does not alter this disorder.     

Selective response mechanism of a platinum disk electrode modified with polyacrylamide membrane conjugated with gallium(III) phthalocyaninate

A non-plasticized polyacrylamide polymer (PAA) coupled with (phthalocyaninato) gallium(III) ([Ga(pc)]⁺), PAA-[Ga(pc)], was first synthesized, and the potentiometric response behavior of this PAA-[Ga(pc)] modified platinum electrode to certain ions was examined in the non-aqueous solvents acetonitrile (AN), dimethylacetamide (DMA), and N-methylpyrrolidinone (NMP). The electrode showed a Nernstian or near-Nernstian response to CN⁻ and F⁻ in AN, DMA, and NMP, but it showed a non-thermodynamic response to Cl⁻and Br⁻ in all the above solvents. Both spectrophotometric and cyclic voltammetric methods were used to investigation the reaction of [Ga(pc)]⁺ with the ions in the solvents. The results revealed that the special selective response phenomena were due to the complex formation reactions of the ions with [Ga(pc)]⁺. The reaction mechanisms were determined on the basis of the shift of the maximum absorption peaks, the appearance of the new peaks on UV-vis spectra for [Ga(pc)]⁺ in the presence of CN⁻ and F⁻ and the clear difference in the redox voltammogram for [Ga(pc)]⁺ at the platinum electrode between the addition of F⁻ and Br⁻ in DMA. There were no obvious differences between the three solvents in terms of their influence on the complexing. It was concluded that the electrode might have applications in obtaining the solubility product of NaF in AN.     

高纯氟化锂的分析

本文叙述了适于作超低损耗金属氟化物光纤材料的高纯氟化锂的方法研究。其分析方法为：氟化锂样品经硝酸溶解，重复蒸发除去大部分Ｆ＾－，以石墨炉原子吸收标准加入法直接测定过渡金属，Ｆｅ，Ｃｏ，Ｃｕ，Ｎｉ含量，制得了四种对光纤质量影响最大的过渡金属杂质的含量均低于０．０００１％的氟化。方法的相对标准偏差为Ｆｅ，４２％，Ｃｏ，１６．８％，Ｎｉ８．８％，Ｃｕ６．９％。     

Paradoxes and paradigms: Observations on pyrohydrolytic decomposition of fluorine-containg materials and accompanying thermochemistry

Pyrohydrolysis is a fast, reliable and convenient method for the decomposition of solid samples. It is widely used for decomposition of samples containing fluorine. The efficiency of different accelerators for pyrohydrolytic decomposition and subsequent determination of fluoride in some raw materials, industrial products and pure CaF₂ was studied. A brief discussion on thermochemistry of these reactions is provided.     

离子色谱法测定米酒中F^—、Cl^—和SO4^2—

研究了用带电导检测器的离子色谱对米酒中F-、Cl-和SO24-进行分离测定的方法.在Dionex HPIC-AS3分离柱上用2.8mmol@L-1NaHCO3-2.2mmol@L-1Na2CO3作流动相进行洗脱,被测组分得到满意的分离,方法简便快速.F-、Cl-和SP24-线性范围分别为0.1～10、0.1～16和0.5～80mg@L～,检出限分别为0.1、0.1和0.5mg@L-1.该法也适用NO-3和NO-2测定.