共查询到20条相似文献,搜索用时 46 毫秒
1.
合成了5种通式为(NH 4) 15[RE(PMo 9V 2O 39) 2]·xH 2O(RE=La 3+,Ce 3+,Gd 3+,Y 3+,Yb 3+)的稀土钼钒磷四元杂多配合物,并用IR,UV,XRD,ICP,TG-DTA和CV等手段对其结构和性能进行了表征.催化活性实验表明,标题化合物对苯酚过氧化氢羟化制苯二酚反应有良好的催化活性. 相似文献
2.
At 25°C, I = 1.0 M (CF 3SO 3−Li ++CF 3SO 3H), [H +] = 0.034–0.274 M and λ = 453 nm, the rate equation for the oxidation of Ti(H 2O), 63+ by bromine was found to be: −d/[Br 2] T/d t= kK/[Br 2][Ti III]/[H +]+ K+ kK/[Br 3−][Ti III]/[H ++ K, where k = 9.2 × 10 −3 M −1 s −1 and K = 4.5 × 10 −3 M. At [H +] = 1.0 M, [Br −] = 0.05–0.4 M, the apparent second-order rate constant decreases as [Br −] increases. The pH-dependence of the oxidation of TiIII-edta by bromine is interpreted in terms of the change in identity of the TiIII-edta species as the pH of the reaction medium changes. The second-order rate constants were fitted using a non-linear least-square computer program with (1/k0edta)2 weighting into an equation of the form: k0edta =k1+k2K1[H+]−1+k3K1K2[H+]−2/1+K1[H+[H+−1+K1K2[H+]−2, with K1 and K2 fixed as earlier determined at 9.55 × 10−3 and 2.29 × 10−9 M, respectively, for the oxidation of bromine. k1=k2=(3.1±0.32)×103M−1s−1 k3=(2.3±0.45)×106N−1s−1. It is proposed that these electron transfer reactions proceed by univalent changes with the production of Br2.− as a transient intermediate. An outer-sphere mechanism is proposed for these reactions. The homonuclear exchange rate for TiIII-edta+TiIV-edta is estimated at 32 M−1 s−1. 相似文献
3.
The highly neutralized ethylenediaminetetraacetate (EDTA) titrant (95–99% as Y 4− anion) precipitates with Ag + cations to form the Ag 4Y species, in aqueous medium, which is well characterized from conductometric titration, thermal analysis and potentiometric titration of the silver content of the solid. The precipitate dissolves in excess Y 4− to form a complex, AgY 3−. Equilibrium studies at 25°C and ionic strength 0.50 M (NaNO 3) have shown from solubility and potentiometric measurements that the formation constant (95% confidence level) β 1 = (1.93 ± 0.07) × 10 5 M −1 and the solubility products are KS0 = [Ag +] 4[Y 4−] = (9.0 ± 0.4) × 10 −18 M 5 and KS1 = [Ag +] 3[AgY 3−] = (1.74 ± 0.08) × 10 −12 M4. The presence of Na +, rather than ionic strength, markedly affects the equilibrium; the data at ionic strength 0.10 M are: β 1 = (1.19 ± 0.03) × 10 6 M −1, KS0 = (1.6 ± 0.4) × 10 −19 M 5 and KS1 = (1.9 ± 0.5) × 10 −13 M 4; at ionic strength tending to zero; β 1 = (1.82 ± 0.05) × 10 7 M −1, KS0 = (2.6 ± 0.8) × 10 −22 M 5 and KS1 = (5 ± 1) × 10 −15 M 4. The intrinsic solubility is 2.03 mM silver (I) in 0.50 M NaNO 3. Well-defined potentiometric titration curves can be taken in the range 1–2 mM with the Ag indicator electrode. Thermal analysis revealed from differential scanning calorimetry a sharp exothermic peak at 142°C; thermal gravimetry/differential thermal gravimetry has shown mass loss due to silver formation and a brown residue, a water-soluble polymeric acid (decomposition range 135–157°C), tending to pure silver at 600°C, consistent with the original Ag 4Y salt. 相似文献
4.
The stability constants of the Cu 2+, Zn 2+, Ni 2+ and Mu 2+ complexes of N-phenyl- o-methoxybenzohydroxamic acid at 30° in 50% v/v aqueous dioxan are: log K1 10·45, 8·16, 7·52, 6·33; log K2 8·90, 6·70, 6·01, 5·59 (for the ions in the order given). 相似文献
5.
本文报道了镧系元素的杂多钨砷酸钾K 11[Ln(AsW 11O 39) 2]·xH 2O(Ln:La、Ce、Pr、Nd、Sm)的合成方法和X-射线粉末衍射、红外及拉曼光谱、X-光电子能谱及有效磁矩的研究结果。 相似文献
6.
The study of fluorescence enhancement has attracted attention recently. For example, the sensitivity and selectivity of Eu-thenoyltrifluoroacetone (TTA)phenan-throline and Eu-diphacinone-ammonia systems in Triton X-100 micelles are increased by the addition of La~(3+) Gd~(3+), Tb~(3+), Lu~(3+) or Y~(3+). The mechanism of this fluorescence(?) 相似文献
7.
合成了通式为K 15H 3[Ce(P 2W 16VO 61) 2]·61H 2O、K 15H 4[Ln(P 2W 16VO 61) 2]·xH 2O(Ln=La 3+,Pr 3+,Nd 3+,Sm 3+,Eu 3+,Gd 3+,Dy 3+,Yb 3+)的9种镧系元素Dawson结构的钨钒磷四元杂多配合物,并用IR、UV、NMR、ESR、XRD、TG-DTA等对其结构和性质进行了研究。该类配合物具有与K 16[Ce(P 2W 17VO 61) 2]·50H 2O类似的结构,对H 2O 2分解有较高的催化活性。 相似文献
8.
研究了N263和TBP为协同载体的液膜体系分离钐和钆的行为.考察了膜相添加剂、内水相反萃剂、外水相盐析剂和膜相中载体浓度对传质分离的影响.当用TBP作为膜相添加剂时,N263能很好地溶解在煤油中.N263-TBP-LMA-1-煤油和NH 4NO 3协同流动载体液膜体系在迁移稀土离子时表现出"倒序"特性,与单纯的N263体系相比,该体系对钐、钆具有较高的选择性. 相似文献
9.
In a constant ionic medium, corresponding to a physiological environment ( Ic = 0.15 mol dm −3 NaCl), the solubilities of anhydrous uric acid, uric acid dihydrate and monosodium urate monohydrate have been measured as a function of p[H] = −log[H +](2-8) and temperature (25°, 32°, 37° and 42°C). The solubility equilibria in the uric acid-sodium urate-water system are discussed on the basis of the solubility constants ( Ks) and the first dissociation constant ( K1) of uric acid and the solubility product ( Ks0) of monosodium urate. The quantities measured in this work are in good agreement with literature values, however, the present solubility data have a much higher precision. 相似文献
10.
The dielectric constants and the elastic coefficients for splay ( K1) and bend ( K3) of the charge transfer induced nematic (N c) phase of tridecyl pentakis(phenylethynyl)phenyl ether ( 1) doped with different amounts of 2,4,7-trinitrofluorenone ( 2) were determined by studying the electric field induced bend deformation using the capacitance method. A negative dielectric anisotropy was observed. For the bend elastic constant K3 values up to 22 × 10 -12 N are found which are one order of magnitude higher than the respective values of discotic nematic (N D) phases. Values of 0·6-0·8 are obtained for the ratio K1/ K3; these show a minimum for the equimolar complex. 相似文献
11.
The ligand monoaza-12-crown-4 ether (A12C4) was studied in aqueous solution at 298 K and an ionic strength of 0.5 mol dm −3 in the presence of an excess of sodium ion (0.5 mol dm −3 NaNO 3). The protonation constant of A12C4, determined by glass electrode potentiometry (GEP) in the same background electrolyte, was found to be log K=9.36±0.03. Polarographic experimental and calculated complex formation curves (ECFC and CCFC) for labile metal–ligand systems, studied at a fixed total ligand (L T) to total metal (M T) concentration ratio and varied pH, were used for the modelling of the metal species formed and the refinement of their stability constants. The metal–ligand model and formation constants are optimised by solving mass-balance equations written for the assumed model and by fitting the CCFC to the ECFC. The CCFC can be generated for any metal–ligand model, including polynuclear metal species, for any L T:M T ratio, and for more than one ligand competing in the complex formation reaction. Three lead complexes with the ligand A12C4, viz. PbL 2+, PbL(OH) + and PbL(OH) 2, were found and their overall stability constants from differential pulse polarography (DPP), as log β, were estimated to be 3.75±0.03, 9.30±0.05 and 12.70±0.05, respectively. Two copper complexes CuL 2+ and CuL(OH) 2 are reported and their stability constants (from DPP) were estimated to be 6.00±0.05 and 21.77±0.1, respectively. Two cadmium complexes CdL 2+ and CdL(OH) + are reported. The stability constant for CdL 2+ was estimated from DPP and GEP as 2.80±0.05 and 2.68±0.03 (the latter value was obtained from a few potentiometric experimental points), respectively, and the stability constant for CdL(OH) + from DPP was estimated to be 7.88±0.05. GEP could not be used for the stability constants determination of other metal complexes studied because of precipitation occurring prior the completion of a complex formation reaction. 相似文献
12.
The exchange constants tor Al 3+ and Fe 3+ ions on the cation-exchange resin Dowex 50W-X8 (H +-form) are reported. A batch method of equilibrium at room temperature was used to determine these constants, which are Al 3+ + 3HR AIR 3 + 3H +, K = 1·66 Fe 3+ + 3HR FeR 3 + 3H +, K = 2·19 R denoting the resin. 相似文献
13.
The acidity constants of benzidine (Bz) in aqueous solutions determined potentiometrically at 25° were Ka1 = (1.11 ± 0.08) × 10 −5, Ka2 = (1.45 ± 0.12) × 10 −4. The apparent mixed constants in 0.1 M sodium nitrate are Ka1 = (5.37 ± 0.28) × 10 −6 and Ka2 = (1.14 ± 0.09) × 10 −4. The ultraviolet spectra were recorded as a function of pH and analysed with these constants to obtain the absorption spectra of H 2Bz 2+, HBz + and Bz; the corresponding wavelengths of maximal absorption are 247, 273 and 278 nm, and molar absorptivities 1.63 × 10 4, 1.76 × 10 4 and 2.26 × 10 4 1.mole −1.cm −1. 相似文献
14.
Because rare earth ions have some characteristics such as narrow spectral width,long fluorescence life, large stokes shift and strongly binding with biological molecules, therefore they are usually as fluorescence probes to study nucleic acids, However the sensitivity is low. It is found that the fluorescence of Tb-nucleic acids (fish sperm DNA and yeast RNA) can increased by Sc 3+,Y 3+,La 3+, Gd 3+ and Lu 3+, among which Gd 3+ and Lu 3+ have the greatest enhancement. This is a newly found co-luminescence effect. 相似文献
15.
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H 3O +(aq) + 1· Na +(nb) 1·H 3O +(nb) + Na +(aq) taking place in the two-phase water–nitrobenzene system (1 = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (H 3O +, 1·Na +) = −0.6 ± 0.1. Further, the stability constant of the 1·H 3O + complex in water saturated nitrobenzene was calculated for a temperature of 25 °C as log βnb (1·H 3O +) = 6.8 ± 0. 2. By using quantum mechanical DFT calculations, the most probable structure of the 1·H 3O + complex species was predicted. In this complex, the hydroxonium ion H 3O + is bound partly to three carbonyl oxygen atoms by strong hydrogen bonds and partly to three alternate phenoxy oxygens by somewhat weaker hydrogen bonds. 相似文献
16.
Formation constants for recrystallized thymol blue were determined in water, using the SQUAD and SUPERQUAD programs. The best model correlating spectrophotometric, potentiometric and conductimetric data was fitted with the dissociation of HL −=L 2−+H +−log K=8.918±0.070 and H 3L 2−=2L 2−+3H +−log K=29.806±0.133 with the SUPERQUAD program at variable low ionic strength (1.5×10 −4–3.0×10 −4 M); and HL=L 2−+H +−log K=8.9±0.000, H 3L 2− =2L 2−+3H +−log K=30.730±0.032, H 4L 2=2L 2−+4H +−log K=32.106±0.033 with SQUAD at 1.1 M ionic strength. 相似文献
17.
Ion-pair formation constants ( KMLA mol −1 dm 3) of Na +– and K +–18-crown-6 ether (18C6) complexes with MnO 4− in water (w) were determined potentiometrically at 25 °C. Simultaneously, extraction constants ( Kex mol −2 dm 6) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 °C were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These Kex values were divided into KMLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate–18C6 extraction systems reported before. 相似文献
18.
The copper (II) or nickel (II) complex formation with two poly(acrylic acids) of high molecular weight (Mw=2.5×10 5 and 3×10 6) was investigated in aqueous dilute solution (NaNO 3 0.1 mol l −1; 25°C). Potentiometric titrations were carried out, first to precise the acid-base properties of the two polymers, and secondly to determine the stability constants of the MA and MA 2 complex species formed. The Bjerrum's method, modified by Gregor et al. (J. Phys. Chem., 59 (1955) 34–39), for the study of polymeric acids was used. The results obtained showed that both polymers present very similar properties. As expected, copper (II) is more readily bound to poly(acrylic acids). CuA 2 was the predominant observed species; the global stability constant log β102 was found to be close to 6.6. With nickel (II), none of the complex species MA or MA 2 becomes predominant (log β102=5.5). Finally, the PAA complexes present a greater stability compared with that of monomeric analogs. 相似文献
19.
液膜分离是近年才发展起来的一种新分离技术 [1]。早在1968年Tosteson [2]就已观察到冠醚化合物在人造膜中对K +、Na +离子的选择性与天然大环化合物在细胞膜中的作用具有共同之处。Cussler [3]曾测定了DB-18-C-6为载体的液膜中一些金属离子的传输通量。Lamb [4]比较了以DB-18-C-6、DT-18-C-6及DKP-18-C-6为载体的氯仿液膜中Pb 2+/Na +、Pb 2+/Ca 2+、Pb 2+/Fe 3+、Pb 2+/Zn 2+的选择比。 相似文献
20.
Determination of the ionic dissociation constants of nitrosyl chloride and dinitrogen tetroxide in sulpholane.A silver chloride—silver electrode is used to study electrochemical systems involving nitrosyl chloride and dinitrogen tetroxide in sulpholane: Ag↓ + NOCl AgCl↓ + NO+ + e- and Ag↓ + NOCl + NO-3 AgCl↓ + N2O4 + e- The dissociation constants of these two NO+ donors determined in this way are: K(NOCl) = 10-11.8 mol l-1 and K(N2O4) = 10-7.2 mol l-1. A titration of N2O4 solutions alone or in the presence of nitric acid is described. This titration is possible in mixtures which contain up to 90% (w/w) nitric acid. 相似文献
|