Dissociation Of Sulfuric Acid Research Articles

Geophysical delineation of acidity and salinity in the Central Manitoba gold mine tailings pile, Manitoba, Canada

Surface electrical and electromagnetic geophysical methods can map enhanced electrical conductivity caused by acid mine drainage in mine tailings piles. In this case study, we investigate quantitative relationships between geophysical responses and the electrical conductivity, acidity and salinity of tailing samples at the Central Manitoba Mine tailings in Manitoba, Canada. Previous electromagnetic surveys at the site identified zones of enhanced conductivity that were hypothesized to be caused by acid mine drainage. In the present study, high-resolution EM31 and DC-resistivity measurements were made on a profile through a zone of enhanced conductivity and laboratory measurements of salinity and pH were made on saturation paste extracts from an array of tailing samples collected from the upper 2m of tailings along the profile.Observed spatial correlation of pH and pore-fluid salinity in the tailings samples confirms that the enhanced conductivity in the Central Manitoba Mine tailings is due to acid mine drainage. Contoured cross-sections of the data indicate that the acid mine drainage is concentrated near the base of the oxidized zone in the thicker parts of the tailings pile. The zone of increased acidity extends to the surface on sloping margins causing an increase in apparent conductivity in shallow penetrating geophysical responses. The quantitative relationship between measured pH and salinity shows that the conductivity increase associated with the acid mine drainage is due only in part to conduction by ions produced from dissociation of sulfuric acid. Comparison of the observations with fluid conductivity estimates based on statistical relationships of pH and ion concentrations in water samples from across the tailings pile shows that Ca2+ and Mg2+ ions also make significant contributions to the conductivity at all values of pH and Cu2+, Al3+ and Fe3+ ions make additional contributions at low pH. Variability in the measured conductivity at constant values of pH is explained by variations in the contribution of the SO42− to the measurements. The results of the study demonstrate the feasibility of using electromagnetic geophysical surveys to map acid mine drainage, and related ionic concentration, in mine tailings.

Influence of pressure (temperature) on the nitric acid distribution between the liquid and vapor in the course of evaporation of nitric acid radioactive waste

Analysis of the published dependences of the HNO3 distribution coefficient between the liquid and vapor in the system with water shows that these dependences are power functions with the exponent depending on the temperature (pressure) and emerge from the azeotropic point. The exponent is inversely proportional to the temperature, and its logarithm is directly proportional to the logarithm of the pressure. The pattern is preserved when a salting-out agent is present in the system and is described similarly when taking into account the hydration and hydrolysis of the cation and the degree of dissociation of sulfuric acid, as shown previously for atmospheric pressure. The dependences obtained are interpreted within the framework of the law of mass action (without activity coefficients) as dilution of the azeotropic compound HNO3(H2O)2 with water with the formation of an associated ionic liquid.

Effect of salting-out agents on nitric acid distribution between liquid and vapor in the course of evaporation of nitric acid radioactive waste

The database on the influence of concentrations of salting-out agents with different cation valence (Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Cu2+, Zn2+, Al3+, Fe3+, La3+, Pu4+, UO22+ nitrates) and of H2SO4 on the HNO3 distribution between liquid and vapor at atmospheric pressure was verified and expanded by performing equilibrium evaporation experiments in an evaporator without reflux with circulation of the bottoms. This equilibrium can be described by the equation \(\log {\kern 1pt} {\alpha _H} = - 2.35 + 2\log \;{X_{\Sigma N{O_3}}}\) (where \({X_{\Sigma N{O_3}}}\) is the total concentration of nitrate ions in aqueous solution), taking into account partial binding of water due to hydration of the salting-out agent and apparent hydrolysis of polyvalent cations, and also incomplete dissociation of sulfuric acid. The suggested model is valid at \({X_{\Sigma N{O_3}}}\) from 3 to 16 M (azeotrope); at \({X_{\Sigma N{O_3}}}{\text{ < }}\;3\), Raoult’s law is observed (αH = const), which is confirmed by a number of examples. In this model, the additivity of the properties of the salting- out agents, taking into account the concentration of “free” water, is assumed, which allows calculation of the composition of the bottoms and distillate when evaporating waste of any composition from radiochemical plants.

Simulations of Acid Dissociation Constants of Polyprotic Acids in Near-Critical and Supercritical Water

This paper reports a molecular dynamics study on the dissociation of sulfuric acid and phosphoric acid in near-critical and supercritical water. pK(a) is known to vary as the temperature and pressure vary, and this variation has important implications for corrosion in supercritical water reaction vessels. This work uses the SPC/E water model and solutes based upon DFT calculations to examine both structural and thermodynamic properties of the dissociation processes. An increase in solute-solvent ordering is observed for larger charges, and this also corresponds to a lower rate of diffusion. All dissociation reactions become less favored with increasing temperature except pK(a1) for sulfuric acid which becomes significantly more favored until 748 K.

Kinetics of acid reactions: making sense of associated concepts

In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four multiple-choice items were developed to determine the understanding of 217 pre-service science teachers of the kinetics of acid reactions that are taught at the Grade 9 to 10 levels in Singapore schools. Each of four items compared two different acid reactions under similar conditions, and respondents were required to select the best graphical representation for the two reactions. Respondents were also required to provide reasons to explain their particular selection for each item. In addition, one item on the dissociation of sulfuric acid and two items involving excess/limiting reagents were also included to provide additional data on the pre-service teachers’ understanding of these concepts that were assessed in the four items on kinetics of acid reactions. The results showed that the pre-service teachers had difficulties in explaining the properties of different common acids, including the dissociation of the acids and how these affect the rates of the different acid reactions. This study highlights the importance of determining pre-service teachers’ understanding of the concepts that they will be teaching with a view to addressing areas of difficulty, as these will have consequences on their future students’ learning.

Interaction of SWCNT and PPTA with sulfuric acid—Compatibilization of two materials in a common solvent

AbstractThe results of a calorimetric study on the melting and crystallization behavior of concentrated sulfuric acid containing dispersed single wall carbon nanotubes (SWCNT), dissolved water, and dissolved poly‐p‐phenyleneterphthalate (PPTA) polymer are presented. The measured reduction of the heat of crystallization is caused by the build‐up of an associated layer of structured acid molecules around SWCNT and PPTA. The freezing point depression is related to the number of dissolved species such as ions. It is shown that this theory accurately describes the experimental data for dissolved water and sulfur trioxide, but not for large molecules such as SWCNT. A mechanism for the interaction between sulfuric acid and SWCNT is proposed, based on preferred adsorption of sulfur trioxide and dissociation of sulfuric acid, leading to an increased number of dissolved low‐molecular‐weight species. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1914–1922, 2008

First-principles molecular dynamics study on aqueous sulfuric acid solutions

The properties of aqueous sulfuric acid have been studied employing density functional theory-based molecular dynamics simulations in conjunction with norm-conserving pseudopotentials. The simulations were carried out for two different concentrations whose molar concentrations were fixed at 0.84 and 10.2 mol/l. The structural features of aqueous sulfuric acid solutions show a strong dependency on the concentration. The Grötthuss-type proton transfer mechanism is not effectively operative at the higher concentration because of the broken hydrogen bond network of water induced by ions generated by the dissociation of sulfuric acid. In addition, to evaluate electrical properties, we carried out a simulation that takes an electric field into account. Results are compared with those of the simulation undertaken with no external electric field.

Influence of Two-step Mechanism of Dissociation of H2SO4 on the Limiting Cathodic Current of Copper Deposition from Sulfate Solutions in Conditions of Natural Convection

The limiting cathodic current of copper deposition at a flat vertical electrode from solutions containing a mixture of copper sulfate and sulfuric acid (in excess) in conditions of natural convection is calculated. The possibility of the two-step dissociation of sulfuric acid is accounted for. The obtained formulas yield the limiting cathodic current at any ratio of bisulfate and sulfate anions in solution.

Water and solute activities in the aqueous H2SO4 -(NH4)2SO4 solutions

The activities of water in H2SO4-(NH4)2SO4-H2O solutions, the concentrations of which ranged from 0.1 to 4.0 mol kg-1 H2SO4 and 0.1 to 5.0 mol kg-1 (NH4)2SO4, were determined by an isopiestic method at 298 K. The experimentally determined water activities showed considerable deviation from the Zdanovskii rule. The activities of water were not in agreement with those calculated from the Robinson-Bower equation, even though the formation of sulfato-complexes of NH4(I) and the dissociation of sulfuric acid were taken into consideration. The behavior of H2SO4-(NH4)2SO4 solu-tions is quite different from other systems. Water activities of aqueous solutions of H2SO4-Li2SO4 and H2SO4-Na2SO4 can be calculated from the Robinson-Bower equation with satisfactory accuracy. The interesting behavior of (NH4)2SO4 can be attributed to the water structure-breaking property of NH4 + ions. An additivity equation for estimating the water activity of aqueous H2SO4 solutions con-taining (NH4)2SO4 was proposed by considering the contributing effects of solutes on the structure of water. The proposed equation satisfactorily described the solution system under investigation. The mean activity coefficients of H2SO4 and (NH4)2SO4 in the solution system, H2SO4-(NH4)2SO4-H2O, at 298 K, were calculated by the McKay-Perring method using the water activities experimentally determined. It is believed that the calculated values for concentrated solutions of more than one sol-ute are sufficiently accurate since the mean activity coefficients of H2SO4 agree with the values measured by the emf method.

Reaction rate and dissociation of sulfuric acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReaction rate and dissociation of sulfuric acidO. Redlich and W. E. GargraveCite this: J. Phys. Chem. 1968, 72, 8, 3045–3046Publication Date (Print):August 1, 1968Publication History Published online1 May 2002Published inissue 1 August 1968https://doi.org/10.1021/j100854a070RIGHTS & PERMISSIONSArticle Views264Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (229 KB) Get e-Alerts

非水溶液滴定による医薬品の定量 (第6報)

Morphine, its derivatives, and their acid salts can be titrated in anhydrous acetic acid with perchloric acid by glass-calomel electrode potentiometrically or with crystal violet as the indicator. Morphine and its derivatives can be determined accurately by the basicity of the methylamino group, and their hydrochloride can also by titrated with same accuracy by adding mercuric acetate more than the equivalent of the sample and the excess of mercuric acetate scarcely hinders the titration. The acidity of phosphoric and sulfuric acids partially augment that of anhydrous acetic acid, so that the determination of the phosphates and sulfates are not very accurate. Codeine sulfate can be titrated one mole as one equivalent, because the first dissociation of sulfuric acid is large, but the second is very small in anhydrous acetic acid. It is known from the titration curves, that the basicity of morphine, ethylmorphine, codeine, hydrocodeine, and 3, 6-diacetylmorphine is similar to each other, but that the basicity of thebaine is stronger than that in anhydrous acetic acid.