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Polarographic reduction of 4-arylhydrazono-1-guanylnitrate-3-methyl-2-pyrazoline-5-ones takes place in a single 4-electron transfer, giving a diffusion controlled irreversible wave in B.R. buffers of pH range 2.0–10.0. The reduction in these compounds takes place at the ?NH?N=C-bond. Effect of various cations, anions and solvent percentage on the reduction has been discussed. The effect of substituents and its correlation with the Hammett substituent constant (δ) have also been studied. 相似文献
13.
Comparative studies of the reaction of 7-arylazo-8-hydroxyquinoline-5-sulphonic acid (Azoxine S) dyes with vanadium(IV), show that 2:1 yellow, water-soluble complexes are formed over the pH range 2.5–6, and that the phenyl derivative is the most suitable for spectrophotometric determination of 0.2–1.4 ppm of vanadium(IV). The colour is formed instantaneously and is stable for about 8 hr. The molar absorptivity at λmax, 400 mμ;, is 1.15 × 104, and the equilibrium constant for complex formation is of the order of 102. These dyes can also be used as indicators in the direct complexometric determination of vanadium(IV). The interference of a number of anions and cations is reported. 相似文献
14.
We show for the first time that a classical Hookean viscoelastic constitutive law for rubbery materials can predict the impact forces and deflections measured with a commercial drop tester when a mass, or tup with a flat impacting surface is dropped onto a flat pad of commercial impact-absorbing rubber. The viscoelastic properties of the rubber, namely the relaxation times and strengths, are obtained by a standard rheological linear-oscillatory test, and the equation of momentum transfer is then solved, using these measured parameters, assuming a uniaxial deflection of the pad during the impact. Good agreement between measured and predicted forces and deflections is obtained for a series of various drop heights, tup masses, impact areas, and pad thicknesses, as long as the deflection of the pad relative to its thickness is small or modest (<50% or so), and as long as the area of the pad is less than or equal to that of the tup. When the pad area is greater than the tup, forces are higher than predicted, unless an empirical factor is introduced to account for the nonuniaxial stretching of the ring of material that extends outside of the impact area. These results imply that the impact-absorbing properties of a rubbery polymeric material can be assessed by simply examining the material's linear viscoelastic spectrum. 相似文献
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The electrochemical oxidation of sulphapyridine at a pyrolytic graphite electrode was studied over a wide pH range. Sulphapyridine is oxidized in an irreversible reaction involving two electrons and two protons to give an electroactive product. On the basis of voltammetric, spectral and coulometric studies and product identification, a tentative mechanism is suggested. 相似文献
18.
Dinesh Kumar Ashu Rani D. S. N. Prasad K. S. Gupta 《Reaction Kinetics and Catalysis Letters》1991,43(1):133-141
The kinetics of the oxidation of 2-furancarboxaldehyde by thallic perchlorate at 50°C obeys the rate law
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Sarika Goyal 《Mathematische Nachrichten》2019,292(10):2189-2202
In this article, we study the eigenvalues of p‐fractional Hardy operator where , , , and Ω is an unbounded domain in with Lipschitz boundary containing 0. The weight function V may change sign and may have singular points. We also show that the least positive eigenvalue is simple and it is uniquely associated to a nonnegative eigenfunction. Moreover, we proved that there exists a sequence of eigenvalues as . 相似文献
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