Mobility Of Hydrogen Ions Research Articles

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

The problem of taking into account the influence of air on the properties of distilled water is considered, namely the lack of a single generally accepted method for calculating such an influence. The sensitivity of the structure of water to the influence of external factors is described and the possibility of recording and studying such factors by changes in the temperature coefficient of electrical conductivity of water is shown. The dependences of the temperature coefficient of electrical conductivity of distilled water on the rate of change in water temperature, the degree of filling of conductometric cells, as well as on the intensity of the exchange of carbon dioxide between water and air across their interface have been studied. It is noted that these metabolic processes are currently insufficiently studied. A hardware-software measuring complex has been developed and manufactured to study the temperature coefficient of electrical conductivity of water when its temperature changes within the range of 20–55 °C. The temperature coefficient of electrical conductivity of water in sealed conductometric cells was measured at different degrees of filling the cells with distilled water and the rate of heating and cooling of water. The degree of filling of the cells varied within the range of 10–100 %, the rate of change in water temperature varied within the range of 0.04–2.00 °C/min. With a constant heating and cooling time of 15 minutes in all experiments, the change in speed was achieved by changing the temperature of the heating element. The integral temperature coefficient of electrical conductivity is calculated based on the initial and final values of electrical conductivity and water temperature in each measurement cycle. The dependences of the temperature coefficient of electrical conductivity on the rate of change in water temperature at several constant degrees of cell filling were obtained. It has been shown that with a constant ratio of the volumes of water and air in the cell and an increase in the rate of heating of water, the temperature coefficient of electrical conductivity of water decreases by 19–22 %. It has been established that at a constant rate of water heating, with a decrease in the volume of water in the cell, the temperature coefficient of electrical conductivity of water decreases by 40–42 %. The results obtained can be used to quantify the dissociation coefficient of carbonic acid, the mobility of hydrogen ions, as well as the intensity of the gas exchange process under various external influences on water. Refinement of data on the electrical conductive properties of water and processes at the water/air interface is necessary for the development of models of atmospheric phenomena and climate change, as well as for the creation of sensors for weak changes in environmental parameters for the purposes of both environmental monitoring and medical diagnostics.

Improvement in energy consumption and operational stability of electrolyte-gated synapse transistors using atomic-layer-deposited HfO2 thin films

Electrolyte-gated transistors (EGTs) are promising candidates for artificial synaptic devices, due to lower energy consumption by forming the electric double layer to modulate the channel conductance. In this work, we propose a three-terminal artificial synapse transistor employing HfO2 electrolyte-gate insulator (EGI). The inorganic HfO2 thin film with high dielectric constant was chosen as a good candidate of an EGI to improve the operational stability and energy consumption for the synapse transistor. Mobile hydrogen ions incorporated in the HfO2 EGI were revealed to be generated during the ALD process at a temperature as low as 100 °C. The synaptic plasticity of the fabricated synapse transistor could be gradually modulated by the movement of mobile ions in the EGI, which were examined to be dependent on the applied pulse conditions. The fabricated synapse transistor emulated biological synaptic functions, including excitatory/inhibitory post-synaptic current (EPSC/IPSC) and paired-pulse facilitation/depression (PPF/PPD). Furthermore, by controlling the pulse spike conditions, the conversion from short-term plasticity (STP) to long-term plasticity (LTP) was successfully verified. The LTP characteristics were demonstrated to be far enhanced with the EGI film thickness by means of magnifying the amounts of incorporated mobile ions. In addition, the long-term reliability and operational repeatability of the fabricated synapse transistor were well verified thanks to the choice of HfO2 EGI. The energy consumption required for single spike event was estimated to be a value as low as 0.26 pJ, thus demonstrating considerable potential as an artificial synapse device.

HYDROLYSIS AND ELECTRICAL CONDUCTIVITY OF METHYLAMONIUM SULFAMATE AQUEOUS SOLUTIONS

The pH-metric, conductometric and spectrophotometric study of the acid-base and electrochemical properties of methylammonium sulfamate aqueous solutions (1·10-4 – 1·10-2 М) in the temperature range 293 – 313 K has been done. The increase in pH and molar conductivity of the studied solutions during their storage over time is explained by the hydrolytic decomposition of sulfamate anions with the formation of sulfate anions and ammonium cations. In the concentration range (0,1 – 1,0)·10-3 М, the degree of hydrolysis of sulfamate anions depends slightly on the initial salt content and reaches 100%. A further increase in the salt content results a directly proportional decrease in the hydrolysis degree. Limit molar conductivity values by Shydlovsky extrapolation are calculated. The influence of the initial concentration of methylammonium sulfamate on the electrochemical properties of aqueous solutions was revealed. The experimental values of the limit molar electrical conductivity of aqueous solutions obtained with an extrapolation of Shidlovsky with an initial concentrations of methylammonium sulfate (1,0 – 10,0)·10-3 М increase with increasing temperature from 293 to 308 K. For solutions with a higher concentration, the values of the limit molar electrical conductivity is independent on temperature and l0 equals 206±19 Om -1 ·sm 2 ·mol -1 . The activation parameters of the conductivity of the investigated solutions at 293 – 313 K were obtained. A relative decrease in the mobility of hydrogen ions in the test solutions was observed, comparable to the valve of the mobility during the transfer along the H-bonds of water. The negative values of ΔS# indicate that the atoms in the activated complexes are located more «compactly» than in the original systems, that is, in the formation of the activated complexes the number of rotational and oscillatory degrees of freedom decreases. The compensatory effects in the activation parameters of the molar electrical conductivity of aqueous solutions of methylammonium sulfamate in the temperature range 293 – 313K are indicated.

Исследование электропроводности спиртовых растворов солей

Electrical conductivity of solutions depends on the nature of the solute and solvent. It is associated with the mobility of ions that are formed during the dissociation of substances in the corresponding solvents. In solvents with large dielectric constant values, substances dissociate into their constituent ions to a greater degree. The dielectric constant of water at room temperature is 78.25. It is a universal solvent and most salts dissolve in it with the decomposition into ions. In proton solvents containing mobile hydrogen ions, salts also dissolve with dissociation into ions. Such solvents include alcohols, the dielectric constant of which is significantly less than the dielectric constant of water. To describe the electrical conductivity of salt solutions in solvents with small dielectric constant, it is proposed to use the Pisarzhevsky-Valden equation in literature. This equation assumes that solvents have a similar chemical nature and the mechanism of salt ion solvation by molecules of different solvents is the same. The degree of solvation changes significantly from one solvent to another for salts containing small ions. This is due to the different solvation of ions in different solvents. Therefore, for such solutions, Pisarzhevsky-Valden equation should not be satisfied. To account for the mechanism of ion solvation in different solvents, A.M. Shkodin proposed an equation that takes into account the dielectric constant of solvent. In this regard the possibility of describing the equivalent conductivity of alcohol solutions of salts with infinite dilution by the equations of Pisarzewski-Valden and Shkodin has been studied in this article. Electrical conductivity of the studied solutions was judged by the specific χ and equivalent to λ electrical conductivities. These two conductivities are related by the equation λ = χ/С, where С is the solution concentration. In this article, for salt solutions of with different concentrations in a certain alcohol, the values of χ and λ were found. By analyzing the dependences 1/λ = f(λС), the values of the limiting equivalent conductivity (λ∞) were found at C = 0. For solutions of each salt in different alcohols, the possibility of describing the obtained values of λ∞ by the Pisarzhevsky-Valden (λ∞· = const) and Shkodin (λ∞· = А·exp(-B/D), where  and D are viscosity and the dielectric constant of alcohol; A, B = const). It was found that the experimental data obtained for solutions of sodium iodite and chlorides of cobalt, iron (3), lithium, calcium, nickel, copper, zinc in alcohols (ethanol, propanol-2 and batanol-1) are better described by the Shkodin equation.

Digital volume tomography in the assessment of mandibular invasion in patients with squamous cell carcinoma of the oral cavity – A prospective study

Cancers in the upper part of aero digestive tract comprises 5% of all the malignancies, most common among them is the squamous cell carcinoma (Acton et al., 2000). The incidence and prevalence of oral squamous cell carcinoma (OSCC) in Indian subcontinent is relatively high because of prevalent habits like chewing tobacco, betel quid and areca-nut which increases the risk of developing OSCC (Feller and Lemmer, 2012). Tumor adjacent to the mandible can invade bone, either by direct extension (Huntley et al., 1996) or by the perineural infiltration (Carter and Pittam, 1980). There are no clear guidance to state the amount of bone resection required beyond the tumor, and in majority of the cases soft tissue extension of the tumor determines the amount of resection (Brown et al., 1994). The decision to maintain the continuity of the mandible demands thorough understanding of the anatomy as well as proper assessment of tumor extension (Huntley et al., 1996). Preoperatively it is difficult to assess the degree of mandibular bone involvement, because there is no single imaging tool available to evaluate the extent of bone invasion 100% accurately (Singh, 2008). Different modalities including clinical examination, plain radiographs, conventional computed tomography (dentascan), magnetic resonance imaging (MRI) and nuclear medicine studies have been studied (Ziegler et al., 2002). Conventional radiographs in the form of orthopantomograph (OPG) provides a decent survey of the mandible, but bone mineral loss should be 30–50% before any change is seen (Huntley et al., 1996, Van Cann et al., 2008) Radionuclide bone scintigraphy utilizing radio-active labeled phosphate compounds along with OPG improves diagnosis in the preoperative evaluation. But this high sensitivity is escorted with very low specificity. Periodontal diseases, infections, infarctions and soft tissue involvement in and around the mandible will show a false positive result (Huntley et al., 1996). MRI is less useful in evaluating the cervical bone involvement due to the absence of signal from cortical bone because of less number of mobile hydrogen ions (Huntley et al., 1996, Boeddinghaus and Whyte, 2008). Digital volume tomography (DVT) is a recent imaging technology. DVT is capable of higher special resolution than dentascan (Genden et al., 2005). So the purpose of this study is to evaluate the diagnostic accuracy of DVT in contrast with OPG, dentascan and histological study in assessing the invasion of mandible of patients with OSCC, clinically adjacent or fixed to the mandible.

The effect of pH on charge inversion and condensation of DNA.

Charge inversion and condensation of DNA in solutions of trivalent and quadrivalent counterions are significantly influenced by the pH value of the solution. We systematically investigated the condensation and charge compensation of DNA by spermidine, hexammine cobalt(iii) (cohex, [Co(NH3)6](3+)) and spermine in solutions of a wide range of pH values from 3 to 9.3 by dynamic light scattering, magnetic tweezers, and atomic force microscopy. In trivalent counterion solution, we found that there is a critical concentration (0.75 mM for cohex and 0.5 mM for spermidine), under which the electrophoresis mobility of DNA initially increases, reaches a maximum, and finally decreases when the pH value is decreased. In contrast, above the critical concentration, the electrophoretic mobility of DNA increases monotonously with decreasing pH value of the solution. The corresponding condensing force has the same dependence on the pH value. However, for the case of quadrivalent counterions, the electrophoretic mobility of DNA is monotonously promoted by lowering the pH value of the solution at any concentration of counterions in which charge inversion of DNA may occur. In atomic force microscopy images and force spectroscopy of magnetic tweezers, we found that maximal charge neutralization and condensation force correspond to the most compact DNA condensation. We propose a mechanism of promoting DNA charge neutralization: small and highly mobile hydrogen ions tend to attach to the DNA-counterion complex to further neutralize its remaining charge, which is related to the surface area of the complex. Therefore, this further neutralization is prominent when the complex is toroidal which corresponds to the case of mild ion concentration while it is less prominent for more compact globules or rod complexes at high counterion concentration.

Proton Presence and Motion in Rhenium-Oxide Films and Their Application to Liquid-Crystalline Cells

Disordered solid phases, containing appreciable amounts of hydrogen ions, are grown at the surface of rhenium oxide crystals, because of the high reactivity of this compound with ambient moisture. To investigate such phenomena, a comparative study is performed on ground powder and thermally evaporated or sputtered films using x-ray diffraction and micro-Raman spectroscopy. Two types of solid phases were found in the films: HxReO3 distorted perovskite structures, based on corner-sharing ReO6 octahedra as in the bulk crystals, and ordered HReO4 crystalline structures, based on tetrahedral perrhenate ions. The complex impedance measurements on ReO3 films support the hypothesis of mobile hydrogen ions in such defective films. Moreover, this relevant protonic conductivity allows the application of these films as active layers inserted into asymmetric nematic liquid-crystalline cells to rectify the electro-optical response of such devices, with performances quite similar to previously studied oxides such as WO3.

Determination of the atmospheric precipitation pH value on the basis of the analysis of lichen cationoactive layer constitution

Studies of equilibria and kinetics of the ion exchange process between the surrounding (water solution) and lichens prove that the number of mobile hydrogen ions bonded in lichens depends on the concentration of hydrogen ions in the precipitation with which the lichens are in contact and the type and concentration of other cations contained in the precipitation. The measurement of these values was suggested; as a result, it enabled to determine the pH of precipitation by determination of mobile cations bonded in exposed or naturally grown lichens. The studies were conducted on Hypogymnia physodes lichens.

Photoactuation from a Carbon Nanotube−Nafion Bilayer Composite

A bilayer composite of single walled carbon nanotubes (SWNTs) deposited onto Nafion exhibits substantial mechanical motion upon exposure to visible or near-infrared light. The magnitude of the actuation parallels the absorption spectrum of the SWNTs in the near-infrared, but the actuation diminishes in the visible and disappears in the UV portions of the spectrum. In the near-infrared region, the photoactuation is linear with respect to the light intensity. The photoactuation also appears to be associated with a photocurrent across the nanotube/Nafion interface. The proposed mechanism for the actuation is that band bending of the semiconducting SWNTs induces polarization of mobile hydrogen ions at the Nafion interface, which then causes swelling of the polymer.

Superprotonic conducting phosphate glasses containing water

Fuel cells using H 2–O 2 offer the potential to minimize atmospheric pollution. Newly developed baria-phosphate glasses containing an appreciable amount of mobile hydrogen ions (protons) as well as molecular water exhibit super proton-conductivity. The new BaO–La 2O 3–Al 2O 3–P 2O 5 glasses exhibit high proton conductivities of 10 −2 S/cm at 200 °C and 10 −3 S/cm at 25 °C with a low activation energy of 0.17 eV. A H 2–O 2 fuel cell using this superprotonic glass electrolyte is operable at temperatures from 25 °C to 200 °C even under non-humidified conditions. The protons in oxide glasses have been often considered for a long time to be almost immobile. However, here we show that these superprotonic conductors of phosphate glasses are a good candidate material for viable electrolytes of fuel cells.

Origin of pH‐Glass Electrode Potentials and Development of pNa‐Responsive Glasses

Generally accepted theories about the origin of the pH response of glasses are based on the assumption that hydrogen ions do not cross the glass membrane. Based on our previous findings that there exist two types of hydrogen ions in glasses, one that is hydrogen bonded and mobile and the other is free of hydrogen bonding and substantially immobile, we proposed that the original presence of mobile hydrogen ions in glasses should be required for the glasses to exhibit the pH response. This proposition was experimentally proved. This indicates that any cations (M), if they are mobile in glasses, should show the pM response. The mobilities of the mobile hydrogen ions in pH‐selective glasses were evaluated to be times higher than those of alkali ions. Thus, the essential condition for glasses to exhibit the pNa response should be that the mobility of hydrogen ions in the glasses should be kept as low as possible compared to that of ions. This suggestion was experimentally verified for a glass in which ions are naturally mobile and ions are much less so. © 2000 The Electrochemical Society. All rights reserved.

Indispensability of the presence of mobile hydrogen ions in glass for its pH response

A commercially available pH-responsive glass specimen with the molar composition of 25Li 2O5BaO3La 2O 37TiO 260SiO 2 was subjected to heat treatment in a vacuum furnace and the pH response of the heat-treated glass specimen was compared with that of the as-received glass. It was found that the heat-treated glass specimen in which the content of “mobile” hydrogen ions was decreased showed a much lower Nernstian slope than the ideal value (59 mV). From these findings, we conclude that the generation of the pH selectivity originates from a hydrogen-ion concentration cell between a solution of a given pH and a glass electrode material and that an essential factor for a glass specimen to exhibit the pH response is that the glass should contain “mobile” hydrogen ions.

Diffusion in dilute aqueous acetic acid solutions at 25�C

A conductimetric technique has been used to measure diffusion coefficients for aqueous solutions of acetic acid at concentrations from 0.002 to 0.02 mol-dm−3 at 25°C. The acetic acid component diffuses more rapidly at lower concentrations where a higher proportion of the slower acid molecules are converted by dissociation to acetate ions and highly mobile hydrogen ions. The observed concentration dependence of the diffusion coefficient verifies the limiting law for weak electrolyte diffusion. A new type of conductimetric diffusion cell with several practical advantages over earlier designs is described together with an improved procedure for the conductimetric determination of accurate diffusion coefficients for weak electrolyte systems.

The heat of dissociation of H5+ derived from measurements of ion mobilities

The mobility of hydrogen ions in hydrogen at 240, 274, and 295 K has been measured over the E/N range 0.5–10 Td and at gas number densities in the range 8×1016–5×1018 cm−3 using a variable length drift tube of the four gauze type. The absolute error and statistical scatter in the mobility values are estimated to be <±0.5% and <±0.15%, respectively. The equilibrium constant for the reactions H3++H2+H2⇄H5++H2 was obtained by fitting to the variation of the measured mobility with gas number density at low E/N values. Checks were made to ensure the reactions were in equilibrium in the drift space. The derived equilibrium constants and the heat of dissociation 250 meV were found to agree with those of Elford and Milloy and to disagree with those of previous workers. Possible causes for the disagreement are discussed. The zero field reduced mobility of a number of impurity ions in H2 at 293 K was measured. The values were as follows (in cm2 s−1 V−1), CH5+ (11.8±0.1), H3O+ (10.5±0.1), N2H+ (12.1±0.1), and H5O2+ (11.0±0.1).

Formation of late sillimanite by hydrogen metasomatism (base-leaching) in some high-grade gneisses

Microstructural evidence indicates that fibrolitic sillimanite partly replaced of the highest-grade metamorphic assemblage in the high-grade metapelitic gneisses, migmatites and granodiorite of the Cooma Complex, southeastern Australia. The sillimanite is interpreted as having formed by the action of mobile hydrogen ions on pre-existing minerals, base cations being released and removed from the sites of reaction. The hydrogen ions may have been liberated during widespread hydration of cordierite. The general base-leaching process may be applicable to the formation of late sillimanite in high-grade, migmatitic gneisses in other areas.

The Mobility of H+3 and H+5 Ions in Hydrogen and the Equilibrium Constant for the Reaction H+3+2H2<=> H+5+H2 at Gas Temperatures of 195, 273 and 293 K

The mobilities of hydrogen ions in hydrogen have been measured by the Bradbury-Nielsen time-offlight method at temperatures of 195, 273 and 293 K, at pressures in the range O' 5-200 torr and at E/ N values ranging from 0�4 to 200 Td. The zero field reduced mobilities of H~ and H~ have been determined to be 1l�18�0�05 and 10'61�0'05cm2 s-1 V-1 at 293K, and 1l�18�0�05 and 10'53�0'05cm2 s-1V-1 at 273�2K respectively. At 194'5K the zero field reduced mobility of H~ was determined to be 10�40�0�05 cm2 s-1V-1 ? The thermal equilibrium constant K. for the reaction H~ + H2 + H2 +2 H~ + H2 was obtained by fitting the mobility data as a function of gas pressure. The values of K. obtained were 1�83�0�45 X 10-18, 2�8�0�7 X 10-18 and 1'6�0'6 x 10-16 cm3 at 293,273 and 195 K respectively. The reduced mobility of Hj as a function of E/N was derived for values of E/ N up to 200 Td from the data taken at gas pressures less than 2 torr and was found to be in good agreement with the data of Miller et al. (1968). The ion species present were identified by the addition of contaminants and by use of supplementary data taken with a drifttube- mass-spectrometer system. The energy for the dissociation of H~ into Hj and H2 was derived by the method of Eyring et al. (1936) and found to be 250� 50 meV.

The complexeng of Ca(II), Co(II), and Zn(II) by polymethacrylic and polyacrylic acid

AbstractAn experimental method proposed for the accurate estimate of the nonideal behavior of metal ions in the course of their complexation by polyacids has been shown to be valid. This nonideal behavior, due to the large and variable electrical field at the surface of the polyelectrolyte in the polyion domain, is ascertained from direct examination of the nonideality of mobile hydrogen ions during potentiometric examination of the competing polyacid dissociation reaction. As a consequence of this approach, it has been possible to show that the dominant complex species in Ca(II)‐, CO(II)‐, and Zn(II)‐polymethacrylic (PMA) and polyacrylic (PAA) acids is an ion pair. The respective formation constants of the ion‐pair species have been determined as well.

Protonic Transport inside Polymeric Membranes

Electrical conductivity σ of sulfonated polystyrene ion-permeable membranes has been measured from 80 to 160°C to determine the effects of glass transition temperature Tg on protonic transport. Membranes were loosely crosslinked (1%) and contained up to 10% by weight of styrene sulfonic acid. Membrane conductivity increases exponentially with rising temperature as given by σ=σ0exp−E/RT where σ0 is the preexponential factor and E is the apparent activation energy for the protonic conduction process. Activation energy values vary from 11.0 to 16.0 kcal/mole in the glassy state and 15.0 to 22.0 kcal/mole in the rubbery state. Self-diffusion coefficients of hydrogen ions within a typical sulfonated membrane above and below its Tg have been computed. The increase in protonic transport with rising temperature has been interpreted to be chiefly due to increasing concentration and mobility of hydrogen ions.

Theory of Secondary Emission of Electrons in Hydrogen

This paper describes a theoretical investigation of the mechanism of ejection of secondary electrons at the cathode surface in electric discharges in hydrogen. Theoretical estimates of the magnitude of the coefficient δ/α (due to photons) are obtained from the energy balance equation of an electron stream moving in a gas under the influence of an electric field. The magnitudes of the coefficient γ (due to ions) are obtained from the theory of resonance neutralization and Auger neutralization and de-excitation of an ion at a metal surface. Comparison is made between such theoretical estimates and those values of γ and δ/α obtained from an analysis of the measurements of the temporal growth of ionization currents. Satisfactory agreement is obtained when the comparison is made at low values of the ratio of the electric field E to gas pressure p (i.e. in the range E/p similar 50 v cm-1 mmHg-1). At larger values of E/p (similar 200 v cm-1 mmHg-1) the agreement is satisfactory only when the mobility of hydrogen ions is taken to be about 20 cm2 sec-1 v-1 when computing γ and δ/α from the experimental data on temporal growth of ionization. This value of the ion mobility is about three times greater than the previously accepted value obtained by linear extrapolation of experimental data for values of E/p < 100 v cm-1 mmHg-1. The separate contributions to the total γ of the various processes of neutralization and subsequent electron ejection from the cathode are estimated over the full range of E/p from 50 to 250 v cm-1 mmHg-1.

Mobility of Hydrogen Ions

Mobility of Hydrogen Ions