530 resultados para Sulphuric acid

em Indian Institute of Science - Bangalore - Índia


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By employing Carstensen's phase-comparison pulse method for measuring ultrasonic velocity-differences, the compressibility of sulphuric acid has been studied anew, the special interest being in the low concentration region. Sulphuric acid is found to show at first a decrease in velocity with increasing concentration and then an increase. The curve representing the apparent molal compressibility Φ(κ̄2) against the square root of the molar concentration c, shows a maximum and a minimum. This anomalous behaviour is interesting in view of the extreme anomalies in other colligative properties of sulphuric acid. A qualitative explanation of the observed maximum and minimum has been suggested.

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Electrooxidation of methanol has been studied in sulphuric acid electrolyte at 60 degrees C on carbon-supported Pt-WO3-x, electrodes employing varying amounts of WO3-x,. It is found that the electrodes containing (3:1) Pt-WO3-x, composite catalyst exhibit a higher catalytic activity towards methanol electrooxidation than platinized carbon electrodes without WO3-x. In the light of the XPS and XRD data on the carbon-supported (3:1) Pt-WOx sample, it is speculated that the WOx is present in the form of an oxyhydroxide, which can promote surface oxy-species on platinum by proton transfer.

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This paper elucidates the methodology of applying artificial neural network model (ANNM) to predict the percent swell of calcitic soil in sulphuric acid solutions, a complex phenomenon involving many parameters. Swell data required for modelling is experimentally obtained using conventional oedometer tests under nominal surcharge. The phases in ANN include optimal design of architecture, operation and training of architecture. The designed optimal neural model (3-5-1) is a fully connected three layer feed forward network with symmetric sigmoid activation function and trained by the back propagation algorithm to minimize a quadratic error criterion.The used model requires parameters such as duration of interaction, calcite mineral content and acid concentration for prediction of swell. The observed strong correlation coefficient (R2 = 0.9979) between the values determined by the experiment and predicted using the developed model demonstrates that the network can provide answers to complex problems in geotechnical engineering.

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The band characteristic of the OH group has been recorded in the Raman spectra of many hydroxides and alcohols. It has not so far been observed, however, in the case of the stronger acids. Using the improved technique of complementary filters recently developed by Ananthakrishnan1, and giving long exposures varying from six to twelve days, I have succeeded in obtaining spectra with sulphuric acid and crystals of iodic, selenious and telluric acids, in which the band is clearly seen in the 4046 A. excitation. Table 1 gives the frequency shifts. The value for boric acid is taken from Ananthakrishnan's paper2.

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A volumetric method for the quantitative determination of Sulphoxides has been developed, based on their oxidation to sulphones by dichromate in presence of 5 M sulphuric acid at 105–110°C. Excess dichromate is titrated by ferrous ammonium sulphate solution. The method is also applicable to the determination of Sulphoxides in metal sulphoxide complexes.

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A new method for the titrimetric determination of perchlorate has been developed, based on its reduction to chloride by iron(II) in a strong sulphuric acid medium at high temperature. The effect of variables, such as the sulphuric acid concentration, the temperature and the period of heating, on the extent of reduction has been studied and the optimal conditions for analytical determination of perehlorate derived.

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ALTHOUGH titanium is determined colorimetrically in aqueous sulphuric acid medium in presence of excess of hydrogen peroxide, the nature of the colour-forming species is not known definitely. Schwarz1 suggested that the colour was due to the peroxo-disulphato titanate anion [O 2Ti(SO4)2]2-. On the other hand, Jahr2 and later Gastinger3 considered that the colour of the compound was due to the peroxy titanyl cation [TiO2 aq.] 2+, and suggested the following equilibrium in solution: Schaeppi and Treadwell4 attributed the colour bo O2TiSO4 or [O2Ti(SO4)2]2-, whereas Babko and Volkova5 represented the coloured complex ion as [Ti(H 2O2)]4+. Mori, Shibata, Kyuno and Ito 6 regarded the coloured species as [TiO2 aq.]2+ or [Ti(OH)2 (H2O)(H2O2)] 2+, assuming the co-ordination number of titanium to be four. Thus, a variety of constitutions has been proposed to explain the colour-forming species of the titanium complex, based on the investigations carried out in dilute sulphuric acid medium, but the complex has not been isolated so far.

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Unlike the analogous case of camphene, hydration of longifolene with acetic acid-sulphuric acid in dioxane, yielded a strongly laevorotatory tricyclic isomer as the main product. At least three sesquiterpene alcohols resulted as side products, one of which could be correlated with longicamphor.

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Chloramine-T has been found to bring about the rupture of S-S link in polythionates in acid medium and oxidise all the sulphur present in the chain into sulphuric acid. Quantitative estimation of a polythionate may be made on the basis of this oxidation reaction.

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Carbon disulphide, on treatment with alcoholic potash, can readily be oxidised quantitatively by chloramine-T, converting all the sulphur to sulphuric acid. Fourteen equivalents of the oxidant are consumed for every mole of carbon disulphide. Since excess of chloramine-T may be determined iodimetrically, this reaction may be used for the determination of carbon disulphide. It may also be applied to the determination of xanthates.

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Solid acid polymer electrolytes (SAPE) were synthesised using polyvinyl alcohol, potassium iodide and sulphuric acid in different molar ratios by solution cast technique. The temperature dependent nature of electrical conductivity and the impedance of the polymer electrolytes were determined along with the associated activation energy. The electrical conductivity at room temperature was found to be strongly depended on the amorphous nature of the polymers and H2SO4 concentration. The ac (100 Hz to 10 MHz) and dc conductivities of the polymer electrolytes with different H2SO4 concentrations were analyzed. A maximum dc conductivity of 1.05 x 10(-3) S cm(-1) has been achieved at ambient temperature for electrolytes containing 5 M H2SO4. The frequency and temperature dependent dielectric and electrical modulus properties of the SAPE were studied. The charge transport in the present polymer electrolyte was obtained using Wagner's polarization technique, which demonstrated the charge transport to be mainly due to ions. Using these solid acid polymer electrolytes novel Zn/SAPE/MnO2 solid state batteries were fabricated and their discharge capacity was calculated. An open circuit voltage of 1.758V was obtained for 5 M H2SO4 based Zn/SAPE/MnO2 battery. (C) 2010 Elsevier Ltd. All rights reserved.

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Electrooxidation of methanol in sulphuric acid on carbon-supported electrodes containing Pt-Sn bimetal catalysts prepared by an in-situ route is reported, The catalysts have been characterized employing chemical analyses, XRD, and XANES data in conjunction with electrochemistry. This study suggests that the Sn content in Pt-Sn bimetals produces: (i) a charge transfer from Sn to Pt and (ii) an increase in the coverage of adsorbed methanolic residues with the Sn content. From the electrode-kinetics data, it is inferred that while the electrodes of (3:3) Pt-Sn/C catalyst involve a 2-electron rate-limiting step akin to Pt/C electrodes, it is shifted to only 1-electron on (3:2) Pt-Sn/C, (3:3) Pt-Sn/C, and (3:4) Pt-Sn/C electrodes.

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Gas-phase controlled absorption of ammonia in foams made of solutions of sulphuric acid has been studied experimentally. Effects of gas-phase concentration of ammonia and type of surfactant on the performance of the foam-bed reactor are investigated. Gas-phase controlled absorption from a spherical bubble is anaylzed using the asymptotic value of Sherwood number (Sh = 6.58), for both negligible as well as significant changes in the volume of the bubble. The experimental data are shown to be in good agreement with the single-stage model of the foam-bed reactor using these asymptotic sub-models, as well as the diffusion-in-sphere analysis available in literature. Influence of effective diffusivity on the time dependence of fractional gas absorption has been found to be unimportant for foam columns with large times of contact. The asymptotic sub-models have been compared and use of the rigid-sphere asymptotic sub-model is recommended for foam columns of practical relevence.