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1.
Boric acid     
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   

2.
Reactions of the ions of La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, and Lu with 3-allylpentanedione (HL) in a water-dioxane (50 vol%) medium were studied by pH-metric titration. Stability constants of LnL2+ and LnL 2 + complexes and pH range where these compounds are mainly formed were determined. The dependence of the stability constants on the atomic number of an element has a characteristic break on the gadolinium ion and shows that the stability of the complexes increases as the size of Ln3+ ions decreases.  相似文献   

3.
Solvation and complexation of Cu(II) and Ni(II) with benzoic (L′), p-methoxybenzoic (L″), and isonicotinic (L) acid hydrazides in aqueous-ethanol solutions (ethanol mole fraction 0.07–0.68) were studied by pH-metry, spectrophotometry, and nuclear magnetic relaxation. The formation constants of the species M(L′)2+, M(L′) 2 2+ , M(L″)2+, M(L″) 2 2+ , M(LH)3+, M(L)2+, M(L)(LH)3+, and M(L) 2 2+ , where M = Cu2+ and Ni2+, were determined. With isonicotinic acid hydrazide, a change in the coordination mode was observed in an isomer of Cu(L) 2 2+ , with one of the ligands coordinating in the bidentate fashion, and the other, in the monodentate fashion via the pyridine nitrogen atom. The suggested structures were confirmed by analysis of the parameters of the ESR and electronic absorption spectra of the complexes. The rate constants of ligand exchange and formation of the complexes Cu(L′)2+, Cu(L′) 2 2+ , Cu(L″)2+, and Cu(L″) 2 2+ in aqueous solutions were determined from nuclear magnetic relaxation measurements; the reactions occur by the associative mechanism. A cyclic process of reduction of Cu(II) to colloidal copper in the presence of L″ and atmospheric oxygen is described.  相似文献   

4.
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   

5.
Crystal chemical properties of lanthanide oxochlorotungstates of composition LnWO4Cl (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) are reported. The unit cell parameters a, b, c, c′, and V of the LnWO4Cl compounds are correlated with lanthanide ionic radii from different radius systems and with the lanthanide atomic number. The ionic radius systems most suitable for describing the crystal chemical properties of the lanthanide oxochlorotungstates are determined.  相似文献   

6.
This work reports the principle, advantage, and limitations of analytical photoion spectroscopy which has been applied to dissociative photoionization processes for diatomic molecules such as H2, N2, CO, and NO. Characteristic features observed in the differential photoion spectra are summarized with a focus on (pre)dissociation of(i) multielectron excitation states commonly observed in the inner valence regions,(ii) shape resonances, and(iii) doubly charged parent ions. Possible origins for negative peaks in the differential spectra are discussed. This spectroscopy is applied to the reported photoion branching ratios for D2 (and H2 at high energies). The main findings are as follows: (1) The direct dissociation of theX 2Σ g + (1sσ g ) state of D 2 + , the two-electron excited state1Σ u + (2pσ u 2sσ g ) of D2, and the2Σ u + (2pσ u ) state of D 2 + appear clearly in the differential spectrum, as previously observed for H2. (2) Decay of H 2 + (D 2 + ) to H+ (D+) above 38 eV is due to the direct dissociation of highly excited states of H 2 + (D 2 + ) such as the2Σ g + (2sσ g ) and high-lying Rydberg states converging on H 2 2+ (D 2 2+ ). (3) In the ionization continuum of H 2 2+ (D 2 2+ ) peculiar dissociation pathways are observed. The differential photoion spectra for O2 derived from the reported photoion branching ratios are also presented. The (pre)dissociation of theb 4Σ g ? ,B 2Σ g ? , III2Π u ,2Σ u ? , and2,4Σ g ? states of O 2 + appears as the corresponding positive values in the spectra in accord with previous observations. Some other dissociation pathways possibly contributing to the spectra are discussed including dissociative double ionization.  相似文献   

7.
Rare gas ions Ne+, Ar+ and Kr+ are injected into a drift tube which is filled with helium gas and cooled by liquid helium. Helium cluster ions RgHe x + (Rg=Ne, Ar and Kr,x≦14) are observed as products. Information regarding the stability of RgHe x + is obtained from drift field dependence of the size distribution of the clusters, and magic numbers are determined. The magic numbers arex=11 and 13 for NeHe x + andx=12 for ArHe x + and KrHe x + . NeHe x + , Ar+ and Kr+ are proposed as the core ions for NeHe 13 + , ArHe 12 + and KrHe 12 + , respectively.  相似文献   

8.
Thermodynamic treatment of the experimental data on the extraction of quadrivalent Pu, U, Th and Zr with tri-n-butyl phosphate (TBP) from nitric acid solutions is presented. It is shown that the extraction of all the quadrivalent metals studied is going according to the same mechanism: M(OH)4?i+(4?i)NO 3 ? +2TBP?M(OH)i(NO3)4?i·2 TBP. For Zr, i=0, 1, and 2; for the remaining M(IV), i=0 and 1. The thermodynamic constants of extraction of M(IV) with the kerosene solutions of TBP according to the above mentioned equation are as follows: Zr: K 0 0 =0.6; K 1 0 =14; K 2 0 =5. Pu: K 0 0 =380; K 1 0 =4.8·104. U: K 0 0 =300; K 1 0 =1.8·104. Th: K 0 0 ~150. It has been established that Zr and Pu(IV) are extracted into 2-thenoyltrifluoracetone (HA) from perchloric acid solutions under the formation of MA4 and M(ClO4)A3 species. For the extraction from nitric acid solutions, the species formed are ZrA4 and Zr(NO3)A3 in the case of Zr, PuA4 and Pu(OH)A3 in the case of Pu. The differences in the qualitative and quantitative characteristics of the extraction of M(IV) with TBP and HA from nitric and perchloric acids are explained by the effect of the character of the acid and of ionic potential upon the structure of the hydration shell of M aq 4+ .  相似文献   

9.
Apparent molar volumes, V ? for glycine (Gly) and glycylglycine (Gly-Gly) in aqueous D(+)-glucose and sucrose solutions have been determined from solution density, ρ measurements at 298.15, 303.15, 308.15, and 313.15 K as a function of the concentration of solutes (Gly and Gly-Gly). The standard partial molar volume, V ? 0 , transfer volume, ΔV ?(tr) 0 , for Gly and Gly-Gly from water to aqueous carbohydrate solutions, partial molar expansibility, E ? 0 , and hydration number, n H of solute have been calculated. The viscosity data have been analyzed by means of Jones-Dole equation to obtain A- and B-coefficients, free energy of activation of viscous flow per mole of solvent, Δμ 1 0# , and solute, Δμ 2 0# , enthalpy, ΔH 0#, and entropy of activation, ΔS 0# of viscous flow were evaluated. The behavior of these parameters has been interpreted in terms of solute-solute and solute-solvent interactions.  相似文献   

10.
An X-ray diffraction study of the single crystals of (C2H7N4O)2[(UO2)2(OH)2(C2O4)(CHO2)2] was carried out. The compound crystallizes in the triclinic system, space group $P\bar 1$ , Z = 2, a = 5.5621(8) Å, b = 8.1489(10) Å, c = 11.8757(16) Å, α = 88.866(7)°, β = 82.204(6)°, γ = 87.378(6)°, V = 532.7(1) Å3, ρcalcd = 2.988 g/cm3. The main structural units in the crystal are the [(UO2)2(OH)2(C2O4)(CHO2)2)]2? chains corresponding to the crystal chemical group A2M 2 2 K02M 2 1 (A = UO 2 2+ , M2 = OH?, K02 = C2O 4 2? , M1 = CHO 2 ? ) of uranyl complexes. The chains are united into a three-dimensional framework through the electrostatic interaction and hydrogen bonds involving uranyl, oxalate, and hydroxyl groups, formate ions, and 1-carbamoylguanidinium cations.  相似文献   

11.
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.
Cluster ions are produced by ion bombardment of thick metal targets and mass selected in a Wien filter. The unimolecular decomposition of Al n + , Cu n + , Mo n + , W n + , and Pb n + is investigated under UHV conditions. The time evolution of the decay allows a glimpse into the cluster formation/fragmentation process. Highly excited metal cluster ions decompose mainly by evaporating single neutral atoms with rates reaching 100%. The collision induced fragmentation (CIF) of stable mass selected metal cluster ions in a low pressure Ar and O2 gas target will be compared to the unimolecular decay.  相似文献   

13.
Guided ion beam mass spectrometry is used to measure the cross sections as a function of kinetic energy for reaction of SiH4 with O+(4S), O 2 + (2Πg,v=0), N+(3P), and N 2 + (2Σ g + ,v=0). All four ions react with silane by dissociative charge-transfer to form SiH m + (m=0?3), and all but N 2 + also form SiXH m + products where (m=0?3) andX=O, O2 or N. The overall reactivity of the O+, O 2 + , and N+ systems show little dependence on kinetic energy, but for the case of N 2 + , the reaction probability and product distribution relies heavily on the kinetic energy of the system. The present results are compared with those previously reported for reactions of the rare gas ions with silane [13] and are discussed in terms of vertical ionization from the 1t 2 and 3a 1 bands of SiH4. Thermal reaction rates are also provided and dicussed.  相似文献   

14.
Partial volumes $\bar V^0$ of amino acids in aqueous NH4Cl and NaCl solutions are discussed. The salts have different effects on water structure. The contributions of the charged NH 3 + and COO? groups of amino acids are found. Structural characteristics of hydrated complexes are calculated: partial volumes of water inside and outside the hydration sphere and hydration numbers. The same value of $\bar V^0$ (NH 3 + , COO?) is achieved at a higher NH4Cl concentration. The two salt systems with the same $\bar V^0$ (NH 3 + , COO?) have similar values of the partial volumes of water and hydration numbers.  相似文献   

15.
Conductivities, densities and ultrasonic speeds measurements of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions of glycine (Gly) and glycylglycine (Gly-Gly) have been made at various temperatures. The critical micelle concentration (CMC), the degree of ionization (??) of the micelles, standard free energy, enthalpy, and entropy of the micellization process (??G m ° , ??H m ° , and ??S m ° ) for the present systems were estimated at different temperatures. The CMC values of HTAB in aqueous Gly and Gly-Gly were also evaluated by density and ultrasonic speed measurements. Apparent molar volumes, (V ?), apparent molar volumes at infinite dilution, (V ? ° ), apparent molar compressibilities, (K ?), of HTAB in the pre- and post-micellar regions, and volume change on micellization (??V ? m ) were also estimated. Large positive values of T??S m ° and small negative values of ??H m ° suggest that micellization process is driven primarily by entropy increase. The increase in ??V ? m and K ? with rise in temperature is indicative of less compact micellar structure of HTAB in presence of amino acid additives. These data suggest that amino acids are solubilised probably in the palisade layer of the micelle.  相似文献   

16.
Metastable ion (MI) and collision-induced dissociation (CID) mass spectra have been recorded and compared for all nine C4H12Si+. isomers. The (Me)4Si+., t-BuSiH 3 +. , s-BuSiH 3 + , and (Me)2EtSiH+. isomers have unique MI and CID mass spectra. The MI mass spectra, including the kinetic energy release values, of (Me)(i-Pr)SiH 2 +. and (Me)(n-Pr)SiH 2 +. are identical, which implies isomerization. MI data also suggest that a fraction of the n-BuSiH 3 +. ions rearrange into branched (Me)2EtSiH+. ions and a fraction of the n-BuSiH 3 +. ions rearrange into branched s-BuSiH 3 +. ions. A comparison with the isomeric C5H 12 +. pentanes reveals a crucial difference: H2 loss occurs for n-BuSiH 3 +. , i-BuSiH 3 +. , s-BuSiH 3 +. , (Me)(n-Pr)SiH 2 +. , (Me)(i-Pr)SiH 2 +. , and Et2SiH 2 +. , but not for any of the C5Hi 12 +. isomers. Generation of four- or five-membered silicon containing rings is suggested for H2 loss from the C4H12Si+. silanes.  相似文献   

17.
In this work, the reactions of ?OH, e aq ? , and SO 4 ?? with diethyl phthalate (DEP) were investigated in aqueous solution by pulse radiolysis, and degradation efficiencies of DEP with ?OH and e aq ? were evaluated in water using steady-state radiolysis as well. The absolute rate constants of ?OH, e aq ? , and SO 4 ?? with DEP were determined as 2.3 × 109, 1.0 × 1010, and 1.0 × 108 M?1 s?1, respectively. The degradation efficiencies for the ?OH and e aq ? reactions were 81 and 33 %, respectively. Transient absorption spectra were observed for the intermediate radicals produced by ?OH, e aq ? , and SO 4 ?? reactions. The results suggested that e aq ? transferred to the ester group, resulting in the formation of DEP radical anions. In contrast, ?OH and SO 4 ?? added predominantly to the aromatic ring of DEP, forming the corresponding ?OH adducts. The fundamental mechanistic parameters and degradation efficiencies derived from these results were significant for evaluations and applications of advanced oxidation processes.  相似文献   

18.
Mass-selected antimony cluster ions Sb n + (n = 3-12) and bismuth cluster ions Bi {ntn} + (n = 3-8) are allowed to collide with the surface of highly oriented pyrolytic graphite at energies up to 350 eV. The resulting fragment ions are analysed in a time-of-flight mass spectrometer. Two main fragmentation channels can be identified. At low impact energies both Sb n + and Bi n + cluster ions lose neutral tetramer and dimer units upon collision. Above about 150 eV impact energy Sb 3 + becomes the predominant fragment ion of all investigated antimony clusters. The enhanced stability of these fragment clusters can be explained in the framework of the polyhedral skeletal electron pair theory. In contrast, Bi n + cluster scattering leads to the formation of Bi 3 + , Bi 2 + and Bi+ with nearly equal abundances, if the collision energy exceeds 75 eV. The integral scattering yield is substantially higher in this case as compared to Sb n + clusters.  相似文献   

19.
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   

20.
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   

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