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21.
实验装置由PVC基管状流通钾离子选择电极和与它结合的流动注射分析体系两部分组成。对该体系的分析特点和影响测定的参数进行了讨论,建立了土壤浸提液中钾测定方法,样品分析结果和火焰光度法有良好一致性。 相似文献
22.
This paper reports the results of a variety of experiments carried out for understanding the solvation behavior of potassium thiocyanate in methanol–water mixtures. Electrical conductivity, speed of sound, viscosity, and FT-Raman spectra of potassium thiocyanate solutions in 5 and 10% methanol–water (w/w) mixtures were measured as functions of concentration and temperature. The conductivity and structural relaxation time suggest the ion–solvent and solvent-separated ion–ion associations increase as the salt concentration increases in the mixtures. The Raman band shifts due to the C–O stretching mode of methanol for the solvent mixtures reveal the formation of methanol–water complexes. The significant changes in the Raman bands for the C–N, C–S and O–H stretching modes indicate the presence of SCN−−solvent interactions through the N-end, “free” SCN− and the solvent-shared ion pairs as potassium thiocyanate is added to the methanol–water mixtures. The relative changes corresponding to H–O–H bending and C–O stretching frequencies indicate that K+ is preferentially solvated by water in these solvent mixtures. The appearance and increase of the intensity of a broad band at ≈940 cm−1 upon salt addition was attributed to the SCN−–H2O–K+ solvent-shared ion pairs. No Raman spectral evidence for K+(H2O)n species was observed. The preferential solvation of K+ and SCN− in the methanol−water mixtures was verified by the application of the Kirkwood−Buff theory of solutions. This theory confirms that K+ is strongly preferentially solvated by water, whereas SCN− is preferentially solvated by the methanol component. 相似文献
23.
油莱甾醇内酯(Brassinolide)(1)是一种高效的植物生长激素,其生理活性与侧链中C_(22)、C_(23)的构型密切相关。当C_(22)、C_(23)为S、S构型时,其活性仅为1的十分之一。在1的 相似文献
24.
Intercalated nanocomposites constituted of poly(butyl methacrylate) (PBMA) as the matrix and an organically modified montmorillonite as the nanosize filler were prepared and rheologically characterized in detail. The rheological behavior of the composites showed dependence on both temperature and clay content. For composites of low clay contents, the steady shear viscosity showed a Newtonian plateau in the low shear rate region at low temperatures and the plateau was replaced by a shear-thinning curve when the temperature was raised. For composites of higher clay contents, strong shear-thinning behavior were observed at all shear rates and all temperatures. The viscoelastic data of the composites showed unusual terminal behavior of a decreasing terminal slope at low frequencies with increasing temperature and clay loading. X-ray diffraction spectra showed that annealing process at higher temperatures shifted the Bragg reflection peaks to a lower angle and broadened the peaks, which provided the evidence for the existence of a temperature-induced solid-like structure that was responsible for the shear thinning and the unusual terminal viscoelastic behavior. 相似文献
25.
26.
Mark Salomon 《Journal of solution chemistry》1990,19(12):1225-1236
Conductivity data are used to determine thermodynamic complex formation constants for cases in which both the initial electrolyte and the complexed electrolyte form ion pairs. Using the method described in the text, the complex formation constants of Li+, Na+ and K+ with the crown ether 18-crown-6 and of Li+ with the ligand triphenylphosphine oxide in propylene carbonate have been evaluated from conductance data. The complexation of AgBr in propylene carbonate solutions of n-etrabutylammonium bromide has also been studied by the measurement of molar conductivities. The results of these studies indicate that ion pairing should not be neglected, even in high permittivity solvents such as propylene carbonate, and that the ion pair association constants correlate well with structural studies on cation-crown ether molecular conformations. 相似文献
27.
Yu. L. Frolov I. V. Guchik V. A. Shagun A. V. Vashchenko 《Journal of Structural Chemistry》2005,46(6):979-984
Models of alkali metal hydroxide-water-dimethylsulfoxide superbasic media have been constructed using Hartree Fock and DFT (B3LYP) quantum chemical methods; the structure and energies of anion complexes are considered. The hydroxide anion in the models is stabilized as complexes of OH?·H2O and OH?· 2H2O types. 相似文献
28.
V. L. Shirokii V. A. Knizhnikov T. P. Konovalov Z. P. Zubreichuk A. A. Erdman S. E. Nefedov I. L. Eremenko A. I. Yanovskii Yu. T. Struchkov N. A. Mayer 《Russian Chemical Bulletin》1993,42(4):732-733
Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded -indenyl--(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993. 相似文献
29.
Electromotive force measurements were carried out on the system KCl–KNO3–H2O at constant total ionic strengths of 0.5, 1.0, 2.0 and 3.0 mol-kg–1 and at 25, 35 and 45°C using a cell consisting of a potassium ionselective electrode and a Ag/AgCl electrode. The Harned coefficients and the Pitzer binary and ternary interaction parameters for the system have been evaluated at each temperature. The osmotic coefficients, excess free energies of mixing and heats of mixing of the system have been predicted at each of the experimental temperatures and ionic strengths. The solubility data at 25°C are also interpreted. 相似文献
30.