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1.
Ibra Gueye Dioum Jacques Vedel Bernard Tremillon 《Journal of Electroanalytical Chemistry》1982,137(2):219-226
Molten potassium tetrachlorogallate and potassium tetraiodogallate were studied in terms of halogenoacidity, based on X? ion-exchange. Titration of KX solution with GaX3 were achieved and characterized by the shift of cathodic voltammetric curves. Autodissociation constants Ki,X/mol2 kg?1 were determined: ?log Ki,Cl=4.25±0.05 and ?log Ki,I=2.6±0.05, as well as the solubility values of KX: 0.41±0.02 and 0.80±0.02 mol kg?1 for KCl and KI respectively. 相似文献
2.
The density of melts of the system KF? K2MoO4? B2O3 was measured. The molar volume in the binary system KF? K2MoO4 deviates only little from the ideal course, which indicates the extended thermal dissociation of the congruently melting additive compound K3FMoO4. In the KF? B2O3 binary system the formation of KBF4 and K2B4O7 leads to the volume expansion, like in the K2MoO4? B2O3 system, where the volume expansion may be described by the formation of the heteropolyanions [BMo6O24]9?. The significant deviation from the ideal behaviour in the ternary system KF? K2MoO4? B2O3 refers to the pronounced interaction, most probably due to the substitution of oxygen atoms in the coordination sphere of the heteropolyanion with the fluorine ones. 相似文献
3.
X-Ray diffraction, infrared, and raman spectroscopic methods were investigated for the detection of K2SO4 in excess of K2S2O7 in solid solutions.The X-ray diffraction lines of K2SO4 were found to be overlapped by the diffraction pattern of K2S2O7 and infrared studies indicated that K2SO4 absorption bands corresponded to regions of strong absorption in K2S2O7. The detection of sulfate could not be carried out by the X-ray diffraction and infrared methods. However, the raman method indicated that a strong and narrow K2SO4 band at 981 cm?1 could unambiguously be used for the detection of sulfate in solid solutions of K2SO4 in K2S2O7, as pyrosulfate showed no absorption around this band. 相似文献
4.
Diogo L. Rocha 《International journal of environmental analytical chemistry》2013,93(13):1389-1401
A flow-based procedure with solenoid micro-pumps was developed for phosphorus fractionation (dissolved organic and inorganic phosphorus) in freshwaters. The spectrophotometric detection was based on the formation of molybdenum blue and the organic species were on-line photo-converted to orthophosphate. The analytical response was linear within 10 and 75?µg?L?1 with a detection limit of 2.0?µg?L?1 (99.7% confidence level). Coefficient of variation of 1.8% (50?µg?L?1 P, n?=?20) and sampling rate of 40 determinations per hour were achieved. Per determination, 160?µg (NH4)6Mo7O24, 10?µg SnCl2, 640?µg K2S2O8 and 10?mg NaOH were consumed, generating 2.0?mL of waste. Slopes of analytical curves obtained for four different organic phosphorus species agreed with those obtained for orthophosphate, indicating quantitative conversion. The results for freshwater samples agreed with those obtained by the AOAC reference procedure at 95% confidence level. The organic matter did not interfere in the photo-oxidative process. The proposed procedure is a fast and environmentally friendly alternative for the phosphorus fractionation in freshwaters. 相似文献
5.
Study and Application of Polarographic Catalytic Wave of Chlordiazepoxide in the Presence of Persulfate 总被引:2,自引:0,他引:2
IntroductionChlordiazepoxide (7 chloro 2 methylamino 5 phenyl 3H 1,4 benzodiazepine 4 oxide)showingpowerfulan tianxietyeffecthasbeenwidelyusedasapsychotherapeu ticdrug .Consequently ,theneedaroseforsensitiveandrapiddeterminationofchlordiazepoxideinblood ,urinean… 相似文献
6.
Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation
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Sebastian Zlotnik Dr. Sulata K. Sahu Prof. Alexandra Navrotsky Prof. Paula M. Vilarinho 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5231-5237
Alkali niobates and tantalates are currently important lead‐free functional oxides. The formation and decomposition energetics of potassium tantalum oxide compounds (K2O?Ta2O5) were measured by high‐temperature oxide melt solution calorimetry. The enthalpies of formation from oxides of KTaO3 perovskite and defect pyrochlores with K/Ta ratio of less than 1 stoichiometry—K0.873Ta2.226O6, K1.128Ta2.175O6, and K1.291Ta2.142O6—were experimentally determined, and the values are (?203.63±2.92) kJ mol?1 for KTaO3 perovskite, and (?339.54±5.03) kJ mol?1, (?369.71±4.84) kJ mol?1, and (?364.78±4.24) kJ mol?1, respectively, for non‐stoichiometric pyrochlores. That of stoichiometric defect K2Ta2O6 pyrochlore, by extrapolation, is (?409.87±6.89) kJ mol?1. Thus, the enthalpy of the stoichiometric pyrochlore and perovskite at K/Ta=1 stoichiometry are equal in energy within experimental error. By providing data on the thermodynamic stability of each phase, this work supplies knowledge on the phase‐formation process and phase stability within the K2O?Ta2O5 system, thus assisting in the synthesis of materials with reproducible properties based on controlled processing. Additionally, the relation of stoichiometric and non‐stoichiometric pyrochlore with perovskite structure in potassium tantalum oxide system is discussed. 相似文献
7.
Pei-Yun Jiang Zhi-Cheng Zhang Man-Wei Zhang 《Journal of polymer science. Part A, Polymer chemistry》1996,34(4):695-699
The kinetics of the K2S2O8-initiated inverse emulsion polymerization of aqueous sodium acrylate solutions in kerosene with Span 80 as the emulsifier has been studied. The conversion-time curves are S-shaped. The following expressions have been obtained for the maximum rate of polymerization and the molecular weight of the polymers under the experimental conditions investigated: Rmax ∞ [K2S2O8]0.78[sodium acrylate]1.5[Span 80]0.1, (OVERLINE)M(/OVERLINE)u ∞ [K2S2O8]−0.37[sodium acrylate]2.9[Span 80]−0.2. The activation energy for the maximum rate of polymerization is 94.8 kJ mol−1. The results suggest a monomer–droplet–nucleation mechanism for the system studied. © 1996 John Wiley & Sons, Inc. 相似文献
8.
The kinetics of the oxidation of S2O32? by ClO2? have been studied in aqueous alkaline solution at 900C using classical titrimetric methods to follow the course of the reaction. The reaction takes place according to the stoichiometry S2O32? + 2ClO2? + 2OH? = 2SO42? + 2Cl? + H2O even in large S2O32? excess. There is some indication of a complex reaction pattern, but 70% of the ClO2? disappearance can be best described by the autocatalytic rate equation -d[ClO2?]/dt = k[S2O32?] [ClO2?] [H+] with k = (1.3 ± 0.2) ×108 M?2 sec?1. The mechanism is explained by postulating nucleophilic attack of S2O32? on HClO2 to form a chlorine-containing intermediate. 相似文献
9.
The potentiometric response of 100-nm spherical K1.3Mn8O16 particles versus K+ ions has been studied in aqueous media using a polymeric technology. The stoichiometry of this material evolves in potassium nitrate solution towards K1.08Mn8O16. A stable and reversible response has been obtained with a sensitivity of 47 mV dec?1 in the range from 8?×?10?5 to 1 mol·L?1, and a rather good selectivity towards Li+, Na+, Mg2+ and Ca2+ $\left( {{\text{log K}}_{{{{\text{K}}^{\text{ + }} } \mathord{\left/ {\vphantom {{{\text{K}}^{\text{ + }} } {{\text{X}}^{n + } }}} \right. \kern-0em} {{\text{X}}^{n + } }}} \approx - {\text{3}}} \right)$ . We assume that this potentiometric response is the result of the ability of K1.08Mn8O16 to specifically adsorb K+ ions. 相似文献
10.
《Physics and Chemistry of Liquids》2012,50(2):218-232
11.
Khalid S. Khairou 《国际化学动力学杂志》2003,35(2):67-72
The kinetics of decomposition of an [Pect·MnVIO42?] intermediate complex have been investigated spectrophotometrically at various temperatures of 15–30°C and a constant ionic strength of 0.1 mol dm?3. The decomposition reaction was found to be first‐order in the intermediate concentration. The results showed that the rate of reaction was base‐catalyzed. The kinetic parameters have been evaluated and found to be ΔS≠ = ? 190.06 ± 9.84 J mol?1 K?1, ΔH≠ = 19.75 ± 0.57 kJ mol?1, and ΔG≠ = 76.39 ± 3.50 kJ mol?1, respectively. A reaction mechanism consistent with the results is discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 67–72, 2003 相似文献
12.
The reactions between aluminium chloride and oxide anion were studied in molten LiCl+KCl eutectic at 470°C. For that purpose, a pO2? indicator electrode made with a membrane in yttria-stabilized zirconia has been used and tested by means of a carbonate ion whose dissociation constant, 10?2.15 atm, was determined. Then, the electrode has allowed us to obtain the formation constant of AlO+ (solvated by Cl?) and the solubility product of Al2O3 (S): 1010.7 and 10?27.4, respectively (molality scale). The equilibrium constant of the following system: 2HCl (g)+O2? agH2O (g)+2Cl? has also been determined: 10?9.93 atm mol kg?1. The conditional solubility of alumina in LiCl+KCl melt is discussed. 相似文献
13.
Dierk Knittel 《Journal of Electroanalytical Chemistry》1985,195(2):345-356
The electrochemical reduction of SO2 in dimethylformamide at Pt electrodes finally leads to the red species S3O2?6 via the blue complex S2O·?4. The UV-VIS absorption coefficients are determined: ?(S2O·?4) = (224 ± 25) × 105 cm2 mol?1; ?(S3O2?6) = (0.64 + 0.07) × 105 cm2 mol?1. A calculation of the complexing constant of SO2 with free SO·?2 radical based on potential shifts confirms this constant to be in the range of 200–700 1 mol?1.Two potentiometric titration methods (viz: with allylbromide and tetraethylammoniumtribromide) for analysis of electrolytically generated SIII-oxo-anions in DMF are presented. Reactions of those anions with aromatic aldehydes and trials for trapping of possibly formed SO are described. 相似文献
14.
The mechanism of catalytic reduction of peroxydisulfate on the palladized aluminum electrode modified by Prussian blue (PB/Pd‐Al) was studied. The charge transfer‐rate limiting step as well as overall reduction reaction of S2O82? is found to be a one‐electron and two‐electron abstraction respectively. The modified electrode is exploited for the hydrodynamic amperometry of peroxydisulfate. It is found that the calibration graph is linear in the S2O82?concentration range 5×10?6–1.5×10?3 mol L?1. The detection limit of the method was 2.4×10?6 mol L?1 S2O82. The method was successfully used for the determination of S2O82? in decolorizing powders 相似文献
15.
Refat M. Hassan 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1147-1151
The kinetics of decomposition of [Alg · Mn VIO42?] intermediate complex have been investigated spectrophotometrically at a constant ionic strength of 0.5 mol dm?3. The decomposition reaction was found to be first-order in the intermediate concentration. The results showed that the rate of reaction was base-catalyzed. The kinetic parameters have been evaluated and found to be ΔS? = ?103.88±6.18 J mol?1 K?1, ΔH? = 51.61 ± 1.02 kJ mol?1, and ΔG? = 82.57 ± 2.86 kJ mol?1, respectively. A reaction mechanism consistent with the results is discussed. © 1993 John Wiley & Sons, Inc. 相似文献
16.
The vulcanization of rubber by sulfur is a large‐scale industrial process that is only poorly understood, especially the role of zinc oxide, which is added as an activator. We used the highly symmetrical cluster Zn4O4 (Td) as a model species to study the thermodynamics of the initial interaction of various vulcanization‐related molecules with ZnO by DFT methods, mostly at the B3LYP/6‐31+G* level. The interaction energy of Lewis bases with Zn4O4 increases in the following order: CO62H43H62S2<1,4‐C5H82O2S3N?CH3COO?. The corresponding binding energies range from ?57 to ?262 kJ mol?1. However, Brønsted acids react with the Zn4O4 cluster with proton transfer from the ligand molecule to one of the oxygen atoms of Zn4O4, and these reactions are all strongly exothermic [binding energies [kJ mol?1] in parentheses: H2O (?183), MeOH (?171), H2S (?245), MeSH (?230), C3H6 (?121), and CH3COOH (?255)]. The important vulcanization accelerator mercaptobenzothiazole (C7H5NS2, MBT) containing several donor sites reacts with the Zn4O4 cluster with proton transfer from the NH group to one of the oxygen atoms of ZnO, and in addition the exocyclic thiono sulfur atom and the nitrogen atom coordinate to one and the same zinc atom, resulting in a binding energy of ?247 kJ mol?1. A second isomer of [(MBT)Zn4O4] with a strong O? H???N hydrogen bond rather than a Zn? N bond is only slightly less stable (binding energy ?243 kJ mol?1). The NH form of free MBT is 36 kJ mol?1 more stable than the tautomeric SH form, while the sulfurized MBT derivative benzothiazolyl hydrodisulfide C7H5NS3 (BtSSH) is most stable with the connectivity >CSSH. 相似文献
17.
SUBALA MONDAL SUMON RAY ANIMESH CHATTOPADHYAY DEBABRATA NANDI ROSHNI SARKAR ALAK KUMAR GHOSH 《国际化学动力学杂志》2014,46(10):587-596
The kinetics of the interactions between three sulfur‐containing ligands, thioglycolic acid, 2‐thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two‐step process in which the first step is ligand‐dependent and the second step is ligand‐independent chelation. Rate constants (k1 ~10?3 s?1 and k2 ~10?5 s?1) and activation parameters (for thioglycolic acid: ΔH1≠ = 22.4 ± 3.0 kJ mol?1, ΔS1≠ = ?220 ± 11 J K?1 mol?1, ΔH2≠ = 38.5 ± 1.3 kJ mol?1, ΔS2≠ = ?204 ± 4 J K?1 mol?1; for 2‐thiouracil: ΔH1≠ = 42.2 ± 2.0 kJ mol?1, ΔS1≠ = ?169 ± 6 J K?1 mol?1, ΔH2≠ = 66.1 ± 0.5 kJ mol?1, ΔS2≠ = ?124 ± 2 J K?1 mol?1; for glutathione: ΔH1≠ = 47.2 ± 1.7 kJ mol?1, ΔS1≠ = ?155 ± 5 J K?1mol?1, ΔH2≠ = 73.5 ± 1.1 kJ mol?1, ΔS2≠ = ?105 ± 3 J K?1 mol?1) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis. A rate law involving the outer sphere association complex formation has been established as 相似文献
18.
Photocatalytic decolorization of methyl orange solution with potassium peroxydisulfate 总被引:1,自引:0,他引:1
Zhong Junbo Ma Di Zhao Hong Lian An Li Min Jiao Huang Shengtian Li Jianzhang 《Central European Journal of Chemistry》2008,6(2):245-252
Increasing environmental pollution caused by toxic dyes due to their hazardous nature is a matter of great concern. It has
been generally agreed that methyl orange (MO) can be effectively degraded in aerated K2S2O8 homogeneous reaction system using near-UV irradiation. In this paper photocatalytic degradation of MO solutions with K2S2O8 was investigated, with particular attention on the possible underlying mechanisms. This report has shown decolorization efficiency
of MO increases with the increasing of the dosage of the catalyst. There is no optimal amount of catalyst in our case, where
special attention was paid on the nature of the photocatalyst itself. The current research revealed that the decolorization
reaction is a pseudo first-order reaction when the concentration of MO is below 20 mg L−1 and the decolorization reaction is zero-order reaction when the concentration of MO is above 100 mg L−1, but the Langmuir-Hinshewood kinetic model does not describe this. The influence of IO4−, BrO3− and H2O2 were investigated in detailed. Several observations indicate that the mechanism is not involved in hydroxyl radical attacks
in MO degradation with K2S2O8 by UV irradiation. The possible underlying mechanisms are direct oxidation of the MO by S2O82− and hydrogen attraction by SO4•−.
相似文献
19.
The stoichiometry of the interaction of Ca2+ with sodium triphosphate was determined using a Ca2+ sensitive electrode, divalent ion sensitive electrode, a glass electrode and by titration calorimetry, A 2:1 and 1:1 complex of Ca2+ and P3O5?10 is found when titrating calcium chloride with sodium triphosphate by the calcium ion sensitive electrode and tritation calorimetry. However, only by titration calorimetry is the 2:1 and 1:1 complex found when titrating sodium triphosphate with calcium chloride. Thermodynamic value (log K, ΔH and ΔS) are reported for the formation of CaP(in3)O?310 and Ca2P3O?10 in aqueous solution. 相似文献
20.
Manometric and potentiometric studies of the oxide ion+oxygen reaction in molten alkali nitrate are reported. Sufficient oxygen was found to be absorbed by alkali nitrate melts after addition of Na2O to convert virtually all of the added O2? ion to O22? and O2? ions. The equilibrium constant and the temperature dependence of the reaction 2 O2?=O2+O22? was determined over a temperature range of 250–400°C. The value of the equilibrium constant determined by the method used was found to depend on whether Na2O, Na2O2, or NaO2 was used as the starting material. Stabilized zirconia tubes were studied for use as oxide ion probes in these melts. In oxygen-containing melts the zirconia/melt interface was shown to respond to added Na2O or NaO2 in a manner similar to the response of a platinum wire dipped into the melt. This response is shown to be the expected one, for the cells studied. When nickel chloride was added to oxygen-saturated melts which contined Na2O, a reaction was found to occur which resulted in the effective loss of two oxide ions from the melt for each nickel ion which was added. 相似文献