共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Sobkowska 《Journal of Radioanalytical and Nuclear Chemistry》1983,78(1):43-51
The results of a study on the polarographic behaviour of TBP and its influence on the determination of uranyl ions is presented. The half-wave potential of the adsorption wave of TBP depends on the concentration of TBP, type of supporting elec trolyte and its concentration. In the presence of TBP the polarographic wave of U(VI) ion is changed. Below 7·10?5 M TBP the polarographic wave of U(VI) is not affected, between 7·10?5 and 2·10?4 M TBP the shape, height and half-wave potential of U(VI) waves are changed and above 2·10?4 M, up to saturated solution of TBP, the waves of U(VI) do, not change further. The bes supporting electrolytes for the determination of U(VI) are KNO3 or NaClO4 in concentrations of 0.1 to 0.5 M, pH 1–2 and TBP concentrations from 3·10?4 to 1.2·10?3 M. 相似文献
2.
《Analytical letters》2012,45(7-8):825-835
Abstract The flow injection technique is shown to provide fast, reliable and sensitive determination of solubility product constants of silver acetate, silver sulfate, silver oxide, silver bromate and silver chloride in microliter volume samples. Potentiometric detection using electrodes of the first kind and second kind was used for measuring silver ions and chloride ions, respectively. The solubilities were determined from measurement of the silver ion concentration in the saturated solutions. In the case of silver chloride, the solubility product constant was calculated from the concentrations corresponding to the intersection of the silver ion calibration curve and the chloride ion calibration curve, i.e., where the potentials of the two electrodes are equal. Tenth-molar sodium nitrate was used for all solutions to maintain constant ionic strength. At a concentration range of 1.00 × 10?2 ? 1.00 × 10?5 M silver, and 1.00 × 10?2 ? 1.00 × 10?4 M chloride, a Nernstian response of 60 m V per decade was obtained. At a sampling rate of 50–70 samples per hour, with 50 μl sample injections, high reproducibility of measurements was achieved, with a -pL 2% relative standard deviation in measured concentrations. The scope and applications of this system are discussed. 相似文献
3.
Rakesh Kumar Mahajan Rajiv Kumar Puri Gagandeep Bawa Tarlok Singh Lobana 《无机化学与普通化学杂志》2008,634(9):1626-1632
A ruthenium(II) complex [Ru(PPh3)2(pytsc)2] {Hpytsc = pyridine‐2‐carbaldehydethiosemicarbazone, (C5H5N)C2(H)=N3‐N2(H)‐C1(=S)N1H} has been used as an ion carrier for the selective determination of silver(I) ions in solution. Silver(I) ion‐selective coated graphite based (CGE) and PVC polymeric membrane based (PME) electrodes exhibit Nernstian slope for silver(I) ions over a wide concentration range from 1.0 × 10−1 M to 5.0 × 10−6 M (with CGE) and 1.0 × 10−1 M to 2.0 × 10−5 M (with PME). The working pH range of these electrodes has been found to be from 1.2 to 7.2 for CGE and 2.2 to 6.5 for PME. The proposed CGE sensor exhibits better analytical features like sensitivity and selectivity towards different secondary ions in comparison to the corresponding PME with no interference from mercury(II) ions . These electrodes also act as indicator electrodes in potentiometric titration and have been successfully used for the determination of silver content in solution of real samples (1 gm dissolved in 100 mL of dilute nitric acid) such as silver ornaments and thin silver foils. Silver content determined by the use of ion selective electrode was found to vary in the concentration range from 1.20 x 10−2 M to 7.45 x 10−2 M and results were found to be comparable with those obtained from the traditional volumetric method of analysis. It is the first report of a metal‐ligand complex used as an ion carrier in ion selective electrode, which is selective for a metal ion other than the one used in the complex. 相似文献
4.
Evan R. Moore Andrew E. Bourne Todd J. Hoppe Philip J. Abode Steven R. Boone Gordon H. Purser 《国际化学动力学杂志》2004,36(10):554-564
The mechanism by which an excess of iron(II) ion reacts with aqueous chlorine dioxide to produce iron(III) ion and chloride ion has been determined. The reaction proceeds via the formation of chlorite ion, which in turn reacts with additional iron(II) to produce the observed products. The first step of the process, the reduction of chlorine dioxide to chlorite ion, is fast compared to the subsequent reduction of chlorite by iron(II). The overall stoichiometry is The rate is independent of pH over the range from 3.5 to 7.5, but the reaction is assisted by the presence of acetate ion. Thus the rate law is given by At an ionic strength of 2.0 M and at 25°C, ku = (3.9 ± 0.1) × 103 L mol?1 s?1 and kc = (6 ± 1) × 104 L mol?1 s?1. The formation constant for the acetatoiron(II) complex, Kf, at an ionic strength of 2.0 M and 25°C was found to be (4.8 ± 0.8) × 10?2 L mol?1. The activation parameters for the reaction were determined and compared to those for iron(II) ion reacting directly with chlorite ion. At 0.1 M ionic strength, the activation parameters for the two reactions were found to be identical within experimental error. The values of ΔH? and ΔS? are 64 ± 3 kJ mol?1 and + 40 ± 10 J K?1 mol?1 respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 554–565, 2004 相似文献
5.
Claude F. Bernasconi Toshiro Iijima Werner Koch Masao Wakae Heinrich Zollinger 《Helvetica chimica acta》1973,56(7):2667-2680
The first and second proton addition equilibrium constants of 1,1-bis-(4′, 4″-dimethylaminophenyl)-ethylene ( 1 ) have been measured by the spectrophotometric method in methanol and in dimethylsulfoxide. Defined as acid dissociation constants of the mono- and diprotonated adduct they are: K1 (CH3OH) = 8.3 (± 0.9) · 10?6M, K2 (CH3OH) = 1.22 (± 0.06) · 10?4M, K1 (DMSO) = 2.3 (± 0.9) · 10?3M, K2 (DMSO) ≥ 1M. The evaluation of the electronic and the NMR. spectra demonstrates that the equilibrium of the two monoprotonated tautomers 2 (methyl-carbenium ion) and 3 (ammonium ion) is, in methanol to about 96% on the side of the ammonium ion (tautomeric equilibrium constant K23 = [3]/[2] ? 23). The tautomer 2 cannot be detected in dimethylsulfoxide. The possible causes of these solvent effects are discussed. 相似文献
6.
A. Aagli N. Tamer A. Atbir L. Boukbir M. El Hadek 《Journal of Thermal Analysis and Calorimetry》2005,82(2):395-399
Summary Solubility of calcium sulfate in concentrated aqueous chloride solutions is of particular significance in chloride hydrometallurgy
and various crystallization processes, such as the production of potassium sulfate from phosphogypsum and potassium chloride.
This paper examines an example of the second type of application in which gypsum and potassium chloride are reacted to form
K2SO4. The solubility of phosphogypsum in aqueous solutions of KCl, HCl, and mixtures of both has first been measured at various
temperatures and concentrations. The parameters investigated are HCl concentration up to 6M, KCl concentration up to 180 g
L-1 and temperature from 25 to 80°C. In addition, the influence of co-existing chloride salts, such as (HCl+KCl), on the solubility
of calcium sulfate is estimated from 25 to 80°C. The solubility increases obviously with the temperature increment as it does
initially with acid concentration, reaching a maximum of about 3M HCl, 130 g L-1 KCl and then drops. At the same time, the solubility of CaSO4·2H2O decreases with increasing KCl concentration. 相似文献
7.
《Journal of Inorganic and Nuclear Chemistry》1976,28(5):1057-1060
Solvent extraction of chromium(VI) from 1 M (H, Na)X solutions and HX solutions at various concentrations (X− = chloride, perchlorate, or nitrate) with trioctylphosphine oxide(E) in hexane has been studied at 25°C. When the hydrogen ion concentration was higher than 10−3 M, the chromium(VI) species in the aqueous phase were H2CrO4 and HCrO4− in all the systems with a chloride complex also present in the chloride system. The extracted species were H2CrO4·E2, H2CrO4·HX·En, and H2CrO4(HX)2·En where n was 2 in the perchlorate and nitrate systems, and 3 in the chloride system. The equilibrium constants for the first acid dissociation and the chloride complex formation in the aqueous phase and the extraction constants for the species in the organic phase were determined. It was assumed that the chromic acid and the mineral acid in the extracted mixed acid species were combined by a hydrogen-bond. 相似文献
8.
Eman M. El-Nemma Hisham S.M. Abd-Rabboh 《International journal of environmental analytical chemistry》2013,93(2):148-158
Cobalt (II) phthalocyanine tetracarboxylate [Co (II)Pc-COOH] has been prepared and used in aqueous solutions as a novel chromogenic reagent for the spectrophotometric determination of cyanide ion. The method is based on measuring the increase in the intensity of the monomer peak in the reagent absorbance at 682 nm due to the formation of a 1 : 2 [Co (II)Pc-COOH] : [CN] complex. The complex exhibits a molar absorptivity (ε) of 7.7 × 104 L mol?1 cm?1 and a formation constant (Kf ) of 5.4 ± 0.01 × 106 at 25 ± 0.1°C. Beer's law is obeyed over the concentration range 0.15–15 µg mL?1 (5.8 × 10?6–5.8 × 10?4 M) of cyanide ion, the detection limit is 20 ng mL?1 (7.7 × 10?7 M) the relative standard deviation is ±0.7% (n = 6) and the method accuracy is 98.6 ± 0.9%. Interference by most common ions is negligible, except that by sulphite. The proposed method is used for determining cyanide concentration in gold, silver and chromium electroplating wastewater bath solutions after a prior distillation with 1 : 1 H2SO4 and collection of the volatile cyanide in 1 M NaOH solution containing lead carbonate as recommended by ASTM, USEPA, ISO and APAHE separation procedures. The results agree fairly well with potentiometric data obtained using the solid state cyanide ion selective electrode. 相似文献
9.
The rate constants 〈σ · υ〉 for collisional de-excitation of the metastable 5D states of Ba+ ions have been determined in an ion trap experiment. TheD-states are selectively populated by pulsed laser excitation of the 6P 1/2 or 6P 3/2 state and the decay at different background pressures is monitored by the change in fluorescence intensity of the excited ions. From the pressure dependence of the decay constants we calculate the de-excitation rate constants for different collision partners, averaged over the velocity distribution of the trapped ion cloud. For He, Ne, H2 and N2 we obtain in the c.m. energy range of 0.1–0.5 eV: 〈σ·υ〉 (He)=3.0±0.2·10?13cm3/s, 〈σ·υ〉 (Ne)=5.1±0.4·10?13cm3/s, 〈σ·υ〉 (H2)=3.7±0.3·10?11cm3/s, 〈σ·υ〉 (N2)=4.4±0.3·10?11cm3/s. The results can be understood qualitatively by a consideration of the ion-atom and ion-molecules interaction potential. 相似文献
10.
Palladium is determined by reaction with tin(II) chloride and rhordamine-6G in hydrochloric acid medium, flotation of the ion-association complex, [(R6G+)2Pd (SnCl?3)4]·[(R6G+) (SnCl?3] with di-isopropyl ether, and dissolution in acetone for spectrophotometry. The molar absorptivity is 2.84 x 105 l mol?1 cm?1 at 530 nm; Beer's law is obeyed in the range 0.05–0.35 μg Pd ml?1. Other platinum metals and silver interfere. Traces of palladium in silver metal are determined after extraction of palladium with dimethylglyoxime in chloroform. 相似文献
11.
L-脯氨酸独有的亚胺基使其在生物医药领域具有许多独特的功能,并广泛用作不对称有机化合物合成的有效催化剂。本文在碱性介质中研究了二(氢过碘酸)合银(III)配离子氧化 L-脯氨酸的反应。经质谱鉴定,脯氨酸氧化后的产物为脯氨酸脱羧生成的 γ-氨基丁酸盐;氧化反应对脯氨酸及Ag(III) 均为一级;二级速率常数 k′ 随 [IO4-] 浓度增加而减小,而与 [OHˉ] 的浓度几乎无关;推测反应机理应包括 [Ag(HIO6)2]5-与 [Ag(HIO6)(H2O)(OH)]2-之间的前期平衡,两种Ag(III)配离子均作为反应的活性组分,在速控步被完全去质子化的脯氨酸平行地还原,两速控步对应的活化参数为: k1 (25 oC)=1.87±0.04(mol·L-1)-1s-1,∆ H1≠=45±4 kJ · mol-1, ∆ S1≠=-90±13 J· K-1·mol-1 and k2 (25 oC) =3.2±0.5(mol·L-1)-1s-1, ∆ H2≠=34±2 kJ · mol-1, ∆ S2≠=-122 ±10 J· K-1·mol-1。本文第一次发现 [Ag(HIO6)2]5-配离子也具有氧化反应活性。 相似文献
12.
Rate constants for the reaction O(3P) + SO2 + M have been determined over the temperature range of 299°–440°K, using a flash photolysis–NO2 chemiluminescence technique. For M?Ar, the Arrhenius expression was obtained. At room temperature k2Ar = (1.05 ± 0.21) × 10?33 cm6/molec2·sec. In addition, the rate constants k2 = (1.37 + 0.27) × 10?33 cm6/molec2·sec, k2 = (9.5 ± 3.0) ± 10?33 cm6/molec2·sec, k3 = (1.1 ± 0.2) ± 10?31 cm6/molec2·sec, and k3 = (2.6 ? 0.9) ± 10?31 cm6/molec2·sec were obtained at room temperature where k3M is the rate constant for the reaction O + NO + M → NO2 + M. The rate data are compared and discussed with literature values. 相似文献
13.
Breakdown graphs have been constructed from charge exchange data for the epimeric 2-methyl-, 3-methyl- and 4-methyl-cyclohexanols. Although the breakdown graphs for epimeric pairs are essentially identical above ~12 eV recombination energy, significant differences are observed for the epimeric 2-methyl- and 4-methyl-cyclohexanols at low internal energies. For the 2-methylcyclohexanols the ratio ([M? H2O]+·/[M]+·)cis/([M? H2O]+·/[M]+·)trans is 3.2 in the [C6F6]+· charge exchange mass spectra. This is attributed to both energetic and conformational effects which favour the stereospecific cis-1,4-H2O elimination for the cis epimer. The breakdown graph for trans-4-methylcyclohexanol shows a sharp peak in the abundance of the [M? H2O]+· ion at ~10 eV recombination energy which is absent from the breakdown graph for the cis epimer. This peak is attributed to the stereospecific cis-1,4-elimination of water from the molecular ion of the trans isomer; the reaction appears to have a low critical energy but a very unfavourable frequency factor, and alternative modes of water loss common to both epimers are observed at higher energies. As a result, in the [C6F6]+· charge exchange mass spectra the ([M? H2O]+·/[M]+·)trans/([M? H2O]+·/[M]+·)cis ratio is ~24, compared to the value of 13 observed in the 70 eV EI mass spectra. No differences are observed in either the metastable ion abundances or the associated kinetic energy releases for epimeric molecules. 相似文献
14.
A multivariate calibration procedure based on singular value decomposition (SVD) and the Ho-Kashyap algorithm is used for the tensammetric determination of the cationic detergents Hyamine 1622, benzalkonium chloride (BACl), N-cetyl-N,N,N-trimethylammonium bromide (CTABr) and mixtures of CTABr and BACl. The sensitivity and accuracy depend strongly on the nature of the detergent. Acceptable accuracy is obtained with a two-step calculation procedure in which calibration constants for the total concentration range of interest are used to guide the choice of a more specific set of calibration constants which are valid for a much smaller concentration span. For Hyamine 1622, concentrations in the range 5 × 10?6?2 × 10?4 M could be determined with an accuracy of ± 10?6 M. For CTABr, these numbers were 3 × 10?6?2 × 10?4 M and ± 5 × 10?7 M; for BACl, they were 2 × 10?3?9 × 10?2 g l?1 and ± 1 × 10?3 g l?1. In the mixtures of CTABr and BACl, the accuracies were ± 3 × 10?6 M and × 1 × 10?3 g l?1, respectively. 相似文献
15.
Chemically Modified Carbon Paste Electrode for Determination of Sulfate Ion by Potentiometric Method
《Electroanalysis》2006,18(16):1598-1604
Four Schiff base complexes of different metal ions, M=Cr(III), Mn(III), Fe(III), and Co(III), were studied to characterize their ability as sulfate ion carriers in carbon paste electrode (CPE). The modified CPE electrode with Schiff base complex of Cr(III), N,N′‐ethylenebis(5‐hydroxysalicylideneiminato) chromium(III) Chloride, showed good response characteristics to SO42? ion. The proposed electrode exhibits a Nernstian slope of 28.9±0.4 mV per decade for SO42? ion over a wide concentration range from 1.5×10?6?4.8×10?2 M, with a detection limit of 9.0×10?7 M. The CPE electrode manifested advantages of relatively fast response time, suitable reproducibility and life time and, most important, good potentiometric selectivity relative to a wide variety of other common inorganic anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 4.0–9.0. The proposed electrode was used as an indicator electrode in potentiometric titration of sulfate with Ba2+ ion, the determination of zinc in zinc sulfate tablet and also determination of sulfate content of a mineral water sample. 相似文献
16.
A composite graphite (CG) electrode modified with poly(2,6‐diaminopyridine) (PDAP) was used as solid state‐ion selective electrode for determination of mercury. The electrooxidation of monomer 2, 6 diaminopyridine (DAP) onto CG was accomplished from the 30 mM DAP in 5% H2SO4 and 0.5 M ZnSO4. The electrode displayed Nernstian response with slope of 28.4±1 mV decade−1 in concentration range of 1×10−6 to 1×10−1 M and in solution of pH 3–5. The limit of detection for electrode was 3×10−8 M with response time of 25 s. The electrode was also suitable as an indicator electrode in the potentiometric titration of Hg2+ with iodide. 相似文献
17.
Alkali-free lead phosphate glasses containing silver chloride have been developed for anion responsive sensors. From measurements of the final glass compositions by electron probe microanalysis, it became clear that some of chloride ions in the glass bulk were not volatilized during the glass melting process. Compared with phosphate glasses containing silver oxide, the new glass electrodes containing silver chloride could respond more rapidly, although the response behaviour for anionic species were similar. From the electrode potential vs. time curve for the anionic species, the potential rapidly reached equilibrium when these concentrations varied from 10?5 to 10?2 M. The response times, t95, to thiocyanate of the new glass electrode and the phosphate glass electrode containing silver oxide were 30 and 110 s, respectively. Moreover, the response time required for an initial potential change with a concentration jump of thiocyanate with the new glass electrode was found to be independent of the membrane thickness within about 2 mm and of the measuring temperature between 15 and 40°C. It is concluded that the diffusion process of species such as silver ion in the glass bulk does not take part in the initial part of the response behaviour. 相似文献
18.
Summary Sorption of nickel, Ni2+, on SiO2 . xH2O (silica gel) has been studied as a function of time conditions: amount of silica gel: 0.10-1.00 g, nickel concentration:
5.00 . 10-5-1.20 . 10-3M, ionic strength: 0.20-1.40M NaClO4, pH 6.50 to 8.50, and temperature 273-318 K. From the kinetic data, the diffusion coefficient of Ni2+ ion was calculated to be 1.28(±0.07) . 10-11 m2 . s-1 under particle diffusion-controlled conditions. The sorption rate was determined as 3.79(±0.35) . 10-3 s-1 at 298 K, pH 8.40 in 0.20M (NaClO4). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Nickel sorption on 0.20
g silica gel decreased with ionic strength from 77.70±0.70% (0.20M NaClO4) to 16.12±0.37% (1.40M NaClO4) at intial pH of 8.50±0.05. A gradual decrease in pH with increasing ionic strength suggests an ion exchange mechanism and
the sorption of Ni2+ on silica gel increasing with temperature indicates an endothermic enthalpy. The effect of different ligands such as fluoride,
carbonate, phosphate and oxalate on Ni2+ sorption on silica gel was studied. 相似文献
19.
Ezio Pelizzetti Edoardo Mentasti Edmondo Pramauro Gianfranco Giraudi 《Analytica chimica acta》1976,85(1):161-168
Catecholamines (adrenaline and L-Dopa) can be determined by a stopped-flow spectrophotometric technique. For individual determinations, catecholamines are oxidized to the corresponding o-benzoquinones by hexachloroiridate(IV). Concentrations in the range 2·10-4–2·10-3 M can be determined with errors of about 2 %. For evaluation of mixtures, aminochromes are formed. The method allows a catecholamine concentration of about 5·10-6 M to be determined in the presence of a ten-fold amount of another catecholamine, with a maximum error of about 10 %. 相似文献
20.
In the pH 7.4 Na2HPO4‐NaH2PO4 buffer solution, the cationic surfactant (CS) interacted with nanogold particles (NG) to form NG aggregations (NGA) that resulted in its color changing from wine red to blue‐violet. NG has a strong catalysis on the formic acid‐phosphomolybdic acid (PMo) colored reaction, but that of the NGA catalysis is weak. With the increase of CS concentration, the NGA increased and the NG decreased, the catalysis decreased and the absorption value at 700 nm decreased linearly. The concentrations of 6.25–250 nmol/L tetradecyl dimethyl benzyl ammonium chloride (TDBAC), 0.625–250 nmol/L cetyltrimethyl ammonium bromide (CTMAB) and 12.5–500 nmol·L?1 dodecyldimethylbenzyl ammonium chloride (DDBAC) had good linear responses to the decreased absorption value (ΔA700 nm), with molar absorption coefficients of 2.2×106, 2.1×106 and 9×105 L·mol?1·cm?1 respectively. This method was simple, highly sensitive and low‐cost. 相似文献