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1.
Hensen Karl Achatz Manfred Müller Rolf Tröbs Ulrich 《Theoretical chemistry accounts》1974,34(4):327-337
Using a one-center-method, treating the inner shells statistically, the valence-shell, however, by quantum mechanics, the equilibrium internuclear distances and total molecular energies have been computed for CH4, SiH4, GeH4, SnH4, PbH4, BH 4 ? , AlH 4 ? , GaH 4 ? , InH 4 ? , TlH 4 ? , NH 4 + , PH 4 + , AsH 4 + , SbH 4 + , and BiH 4 + . The results are in good agreement with experimental data as well as with theoretical values. 相似文献
2.
pH ranges of existence of boric acid and its ionic species H2BO 3 ? , HBO 3 2? , BO 3 3? , and B(OH) 4 ? in aqueous solutions are calculated using Mathcad software package. 相似文献
3.
The aqueous chemistry of phosphorus is dominated by P(V), which under typical environmental conditions (and depending on pH and concentration) can be present as the orthophosphate species H3PO 4 0 (aq),H2PO 4 ? (aq),HPO 4 2? (aq) or PO 4 3? (aq). Many divalent, trivalent and tetravalent metal ions form sparingly soluble orthophosphate phases that, depending on the solution pH and concentrations of phosphate and metal ions, can be solubility limiting phases. Geochemical and chemical engineering modeling of solubilities and speciation require comprehensive thermodynamic databases that include the standard thermodynamic properties for the aqueous species and solid compounds. The most widely used sources for standard thermodynamic properties are the NBS (now NIST) Tables (from 1982 and earlier, with a 1989 erratum) and the final CODATA evaluation (1989). However, a comparison of the reported enthalpies of formation and Gibbs energies of formation for key phosphate compounds and aqueous species, especially H2PO 4 ? (aq) and HPO 4 2? (aq), shows a systematic and nearly constant difference of 6.3 to 6.9 kJ?mol?1 per phosphorus atom between these two evaluations. The existing literature contains numerous studies (including major data summaries) that are based on one or the other of these evaluations. In this report we examine and identify the origin of this difference and conclude that the CODATA evaluation is more reliable. Values of the standard entropies of the H2PO 4 ? (aq) and HPO 4 2? (aq) ions at 298.15 K and p?° =1 bar were re-examined in the light of more recent information and data not considered in the CODATA review, and a slightly different value of S m o (H2PO 4 ? , aq, 298.15 K) = (90.6±1.5) J?K?1?mol?1 was obtained. 相似文献
4.
M. Horn S. Seeger R. Oswald P. Botschwina 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,36(3-4):293-299
The vibrational structure of the first band of the photoelectron (PE) spectrum of HO 2 ? and DO 2 ? has been calculated on the basis of (slightly modified) ab initio potentials. The best agreement with the experimental spectrum of HO 2 ? is obtained for a vibrational temperature of ca. 600 K. “Peak D”, which has been under debate in earlier work, is composed of two transitions, with the “hot” transition 3 1 1 being more intense than the adiabatic transition. Since thev 2 bending mode of DO2 has significant OO stretching character, the vibrational structure of the PE spectrum of DO 2 ? is more complex than that of HO 2 ? . Large-scale RCCSD(T) calculations of the equilibrium electron affinity of HO2 yield 1.058 eV which agrees with the experimental value of 1.044 ± 0.020 eV. 相似文献
5.
O. I. Shchukina A. V. Zatirakha A. D. Smolenkov O. A. Shpigun 《Moscow University Chemistry Bulletin》2014,69(4):168-174
To increase the efficiency of anion exchangers based on copolymers of styrene and divinylbenzene in ion chromatography a new method for spatial separation and hydrophilization of functional groups using epichlorohydrin is suggested. Synthesis consists of acylation of a matrix by acetic anhydride, reductive amination by methylamine hydrochloride, alkylation of the aminated phase using epichlorohydrin, amination by dimethylamine at the terminal chlorine atom, and quaternization of the terminal amino group with epichlorohydrin. The obtained anion exchangers make it possible to simultaneously determine eight anions (F?, HCOO?, Cl?, NO 2 ? Br?, N 3 ? HPO 4 3? and SO 4 2? ) and demonstrate high efficiency (more than 62000 N/m for HPO 4 2? ) in a suppressed ion-chromatography mode. 相似文献
6.
Horst Müller 《Analytical and bioanalytical chemistry》1969,247(3-4):145-149
The ions ReBrnCl 6?n 2? (0?n?6) and OsBrnCl 6?n 2? , respectively, ReO4 ? and Br? have been separated on cellulose using the thin-layer chromatographic technique with 3.2 M sulphuric acid as the mobile phase. 相似文献
7.
Ning Chen Sijian Gao Jichuan Huo Haibin Wang Jichuan He Yongchang Zhu 《Journal of Thermal Analysis and Calorimetry》2014,116(2):875-879
High-temperature thermal transformation of aluminum–chromium phosphates has been investigated by means of DSC–TG, IR, and XRD analysis. The relative dielectric constant and thermal decomposition were measured and discussed. The results show that crystallization and thermal decomposition started at about 1,273 K, only AlPO4 and Cr2O3 have been found at 1,873 K due to the decomposition of PO 3 ? , P2O 7 2? , and PO 4 3? . The relative dielectric constant is fluctuant. 相似文献
8.
E. V. Elipasheva A. S. Kamasheva P. N. Kulikov G. M. Sergeev 《Journal of Analytical Chemistry》2013,68(7):590-594
A method is proposed for the selective photometry determination of perchlorates in potable water with a detection limit of 2×10?3 mg/L is proposed based on the extraction of its ion pair with the astrafloxin cation and absorbance measurements at 540 nm. The following ratios of matrix ions are acceptable (in parentheses): ClO?, ClO 2 ? , ClO 3 ? , BrO 3 ? (500); I? (1000); IO 3 ? (7000); HCO 3 ? , Cl?,SO 4 2? , NO 3 ? , Br?, Na+, K+, Ca2+, Mg2+ (10000). The relative error of determination for ClO 4 ? is 20% in the range 4 × 10-3-1 × 10?2 mg/L and 10% in the range 1 × 10-2–5 × 10?2 mg/L. 相似文献
9.
Adsorption studies of the removal of anions from aqueous solutions onto an adsorbent prepared from wheat straw 总被引:1,自引:0,他引:1
Modified wheat straw (MWS) was prepared by the grafting of epichlorohydrin, triethylamine and ethylenediamine onto WS. The characteristics of MWS and its adsorption capacity for NO 3 ? , PO 4 3? and Cr2O 7 2? were investigated. The results indicate that amine groups with positive charge have been introduced into the structure of MWS, and significantly increased its anion adsorption property. The functions of MWS dosage, the solution pH, the contact time and temperature have significant influence on the adsorption process, and the adsorption is well fitted with the Langmuir equation and pseudo second-order model. The maximum adsorption capacity of MWS for NO 3 ? , PO 4 — (P) and Cr2O 7 2? (Cr) is 53.5, 62.4 and 386.2 mg g?1, respectively. 相似文献
10.
A. Zielenkiewicz 《Journal of Thermal Analysis and Calorimetry》1995,45(4):811-821
The results of calorimetric studies of 5SrRNA solutions isolated from lupin seeds in the pressence of the ClO 4 ? , NO 3 ? , Br 4 ? , SO 4 2? , Cl?, COO? (maleic and fumaric acids) anions were reported. The plots of calorimetric curves, enthalpy of conformational changes of two state transitions were presented. Using the deconvolution method proposed by Freire and Biltonen the elementary transitions were distinguished and discussed. 相似文献
11.
L. N. Polyshchuk E. S. Yanovskaya V. V. Yanishpol’skii V. A. Tertykh K. M. Sukhoi M. V. Burmistr 《Russian Journal of Applied Chemistry》2007,80(9):1590-1593
The sorption of polyionene 1,4-MePh on the silica gel surface was studied. The silica gel modified with polyionene sorbed was used for sorption preconcentration of MoO 4 2? , WO 4 2? , Cr2O 7 2? , and VO 3 ? anions from aqueous solutions. The sorption isotherms of these anions on the initial and modified silica gels were obtained and analyzed. 相似文献
12.
R. Keil 《Analytical and bioanalytical chemistry》1976,281(2):123-124
Perbromate is reduced to bromate by iodide in weakly alkaline solution (pH 7–9) at 100° C. The formation of iodine in the hot solution is prevented by addition of an excess of arsenite, which is finally titrated with a I2-solution for the determination of BrO 4 ? . The total BrO 3 ? content is then determinated by titration of the acidified solution with thiosulphate. From both titrations the initial content of BrO 3 ? is obtained. Both methods are simple and accurate. A direct method for the determination of BrO 3 ? in solutions containing BrO 4 ? is also described. 相似文献
13.
Yan Xiaoju Bao Ruiling Yu Shuili 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(8):1318-1325
The article studies on the effects of six inorganic ions (Ca2+, Mg2+, Cl?, SO 4 2? , H2PO 4 ? , and HCO 3 ? ) on titanium dioxide (TiO2)-based photocatalytic degradation of humic acid (HA). We focus on the effects of the inorganic ions on HA characters, adsorption of HA on TiO2 and photocatalytic degradation of HA. The results indicate that Ca2+ and Mg2+ with HA can form complexes which can decrease the solubility of HA, and then increase the HA adsorbed on TiO2. However, the complex is more difficult to be degraded than HA. The effects of Cl? and SO 4 2? are closely related to their influences on HA solubility. The solubility changes of HA to some extent can enhance the adsorption of HA on TiO2, and promote the photocatalytic degradation. Nevertheless, great solubility decreasing of HA can weaken the photocatalytic degradation. HCO 3 ? and H2PO 4 ? can inhibit the photocatalytic degradation process seriously, because HCO 3 ? and H2PO 4 ? are the strong scavengers of hydroxyl radicals, and can weaken the adsorption of HA on TiO2 due to adsorption competition. 相似文献
14.
A. L. Chistyakov I. V. Stankevich N. P. Gambaryan I. S. Akhrem 《Russian Journal of Organic Chemistry》2006,42(11):1606-1614
Simulation of fragments of potential energy surface for systems CH4 + CBr 3 + , CH4 + CBr 3 + AlBr 4 ? , CH4 + CCl 3 + AlCl 4 ? , and CH4 + CCl 3 + Al2Cl 7 ? was performed by DFT-B3LYP and DFT-PBE methods. The important role of nucleophilic assistance in methane halogenation by these superelectrophiles was confirmed. These reactions occur with a synchronous hydride transfer from methane to the electrophile within the cyclic transition states in linear C-H-C fragment of the rings and a generation of a C-Hlg bond between the carbon atom of the arising methyl group and the halogen atom of the electrophile. The nucleophilic assistance from the unshared electron pair of this halogen atom provides the lowering of the potential barriers to methane halogenation by complexes CBr 3 + AlBr 4 ? , CCl 3 + AlCl 4 ? , and CCl 3 + Al2Cl 7 ? to the values of the order of 20 kcal mol?1. These essential features of the mechanism of methane halogenation are independent of the halogen nature and are retained on going from the model electrophiles to the real ones. 相似文献
15.
Primary processes in the reduction of p-nitroacetophenone (p-NAP) by ascorbic acid (AA) in water photosensitized by thiacyanine dimers M 2 2? have been considered. For M 2 2? , the quantum yields of fluorescence and intersystem crossing to the triplet state (M 2 2? )T increases in comparison to the monomers M?. The dimers (M 2 2? )T enter into the reactions of both one-electron photoreduction by ascorbic acid to give AA+· and M 2 3? and one-electron photooxidation by p-nitroacetophenone to give p-NAP?· and the dimeric radical anion M 2 ? which dissociates to M? and M· within 25–30 μs. The primary oxidative or reductive photosensitization in the ternary systems containing (M 2 2? )T, p-NAP, and AA affords p-NAP?· and AA+·. 相似文献
16.
T. V. Aksenova A. N. Petrov V. A. Cherepanov L. Ya. Gavrilova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(8):1215-1220
The oxygen nonstoichiometry δ of lanthanum cobaltite doped with acceptor impurities (Sr and Ni), La1 ? x SrxCo0.9Ni0.1O3 ? δ (x = 0.1, 0.3), was studied by high-temperature thermogravimetry over the temperature and pressure ranges 723 K ≤ T ≤ 1373 K and 10?3 atm ≤ $p_{O_2 } $ ≤ 1 atm. The partial replacement of cobalt with nickel and lanthanum with strontium increased the oxygen nonstoichiometry δ. The partial molar enthalpies $\Delta \bar H^\circ _O $ and entropies $\Delta \bar S^\circ _O $ of solution of oxygen in the solid phase were calculated. Models of point defect formation were suggested and analyzed. The equilibrium constants of formation and concentrations of predominant point defects, ionized oxygen vacancies V o .. , holes Me Co . (Co Co . and Ni Co . ), and electrons Me Co ′ (Co Co ′ and Ni Co ′ ) localized on 3d transition metals, were determined by nonlinear regression from the experimental and theoretical logp $p_{O_2 } $ ?δ dependences. 相似文献
17.
The solubility of carefully characterized magnetite, Fe3O4, in dilute aqueous solutions saturated with H2 has been measured at temperatures from 100 to 300°C in a flow apparatus. Solution compositions included either HCl or NaOH molalities of up to 1 and 40 mmole-kg?1, respectively, and H2 molalities of 0.0779, 0.779, and 8.57 mmole-kg?1. The dependence of the equilibrium solubility on the pH and reduction potential were fitted to a scheme of soluble ferrous and ferric species consisting of Fe2+, FeOH+, Fe(OH)2, Fe(OH) 3 ? , Fe(OH)3, and Fe(OH) 4 ? . Solubility products from the fit, corresponding to the reactions $$\tfrac{1}{3}Fe_3 O_4 + (2 - b)H^ + + \tfrac{1}{3}H_2 \rightleftharpoons Fe(OH)_b^{2 - b} + (4/3 - b)H_2 O$$ and $$\tfrac{1}{3}Fe_3 O_4 + (3 - b)H^ + \rightleftharpoons Fe(OH)_b^{3 - b} + \tfrac{1}{6}H_2 + (4/3 - b)H_2 O$$ were used to derive thermodynamic constants for each species. The extrapolared value for the Gibbs energy of formation of Fe2+ at 25°C is ?88.92±2.0 kJ-mole?1, consistent with standard reduction potentials in the range Eo(Fe2+)=?0.47±0.01 V. The temperature coefficient of the equilibrium Fe molality, (?m(Fe, sat.)/?T)m(H2).m(NaOH), changes from negative to positive as the NaOH molality is increased to the point where Fe(OH) 3 ? and Fe(OH) 4 ? predominate. 相似文献
18.
N. V. Bausk S. B. Érenburg L. G. Lavrenova L. N. Mazalov 《Journal of Structural Chemistry》1995,36(6):925-931
EXAFS spectroscopy is used to investigate the characteristic features of the spatial and electronic structure of the polynuclear Fe(II) complexes Fe(ATR)3A2 (where A is the NO 3 ? , BF 4 ? , Br?, or ClO 4 ? anion and ATR is 4-amino-1,2,4-triazole) and their magnetically diluted phases FexZn1?x(ATR)3(NO3)2. The absolute distances from Fe and Zn to the surrounding atoms are determined at temperatures higher and lower than the spin transition point. In all complexes, the spin transition is accompanied by significant changes in the local environment of Fe atoms, while in the magnetically diluted phases the surrounding of zinc remains unchanged. It is shown that addition of Zn atoms distorts the triazole rings in the low-spin state of the complexes. No localized anions were revealed within 3.3 Å from the Fe and Zn atoms. It is shown that a decrease in the spin transition temperature correlates with an increase in Fe?N distances in the low-spin complexes due to magnetic dilution and substitution of anions in the series NO 3 ? , BF 4 ? , Br?, ClO 4 ? of ATR-containing complexes. 相似文献
19.
E. Ianovici M. Kosinski P. Lerch A. G. Maddock 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):315-326
The photochemical decomposition of (NH4)2TcCl6 in dilute HCl, HClO4 and H2SO4 solutions has been studied. Electrophoresis and spectrophotometry were used to identify TcCl 6 2? , TcCl5 (H2O)?, cationic and uncharged species and TcO 4 ? . The yield of each species as a function of the time of uv irradiation was determined. The TcCl 6 2? , yield decreases to zero after 50 h of irradiation. The TcCl5(H2O)?, cationic and uncharged species and TcO 4 ? are formed in different proportions in the three acids. After 120 h of irradiation of the HCl solution the principal Tc species was the cationic one (≈70%) followed by the uncharged species (≈24%). In HClO4 solution the cationic species (≈70%) was followed by TcO 4 ? , but in H2SO4 solution the uncharged species amounts to ≈90%. 相似文献
20.
M. R. Bissengaliyeva L. P. Ogorodova L. V. Mel’chakova M. F. Vigasina 《Journal of Thermal Analysis and Calorimetry》2012,109(1):467-471
Thermal and thermochemical investigations of natural hydroxyl-bearing copper sulfate Cu3SO4(OH)4??antlerite have been carried out. The stages of its thermal decomposition have been studied employing the Fourier-transform IR spectroscopy. The enthalpy of formation of antlerite from the elements ??f H m o (298.15?K)?=?(?1750?±?10)?kJ?mol?1 has been determined by the method of oxide melt solution calorimetry. Using value of S m o (298.15?K), equal to (263.46?±?0.47)?J?K?1?mol?1, obtained earlier by the method of adiabatic calorimetry, the Gibbs energy value of ??f G m o (298.15?K)?=?(?1467?±?10)?kJ?mol?1 has been calculated. 相似文献