Hydrogen Ion Activity Research Articles

Investigation of Metrological Characteristics of Buffer Solutions in pH Measurements

The metrological characteristics of buffer solutions prepared from high-purity substances were investigated. The possibility of using them in metrological studies conducted on the State Primary Standard of the рН activity of hydrogen ions in aqueous solutions GET 54–2011 was appraised.

Galena Non-oxidative Dissolution Kinetics in Seawater

The rate of non-oxidative galena dissolution in seawater compositions over the pH range of 2–4.5 was determined from batch reactor experiments. The derivative at zero time of a polynomial fit of the Pb concentration versus time data for the first 30 min was used to determine the rate. A plot of RGn (rate of galena dissolution) versus pH for data from six experiments is linear (R2 = 0.96), with a slope of 0.5. The rate equation describing the rate of galena dissolution as a function of hydrogen ion activity is $$R_{\text{Gn}} = - \,10^{ - 10.72} \left( {a_{{{\text{H}}^{ + } }} } \right)^{0.50}$$ Varying the concentration of dissolved oxygen produced no significant effect on the measured rates. The activation energy, based on four experiments carried out over the temperature range of 7–30 °C, is 61.1 kJ/mol.

Rate equations for modeling carbon dioxide sequestration in basalt

Dissolution rate equations are developed from published data for glassy and crystalline basalt to predict the silica release flux (JSi) as a function of hydrogen ion activity (2 < pH < 12) and temperature (0° < T < 100 °C). For glassy basalt the silica flux isJSi=(5.00×102)e(−39700R)1TaH+1.01+(5.26×10−5)e(−38400R)1TaH+−0.258and for crystalline basalt the silica flux isJSi=(7.40)e(−40100R)1TaH+0.680+(8.67×10−7)e(−32900R)1TaH+−0.286.These rate equations are implemented in TOUGHREACT to simulate a CO2 saturated solution reacting with glassy and crystalline basalt in batch and semibatch reactors. The crystalline basalt models are compared with a more complex basalt representation comprising a composite mixture of olivine, plagioclase and pyroxene dissolution rates. Results show that numerical models based on the newly developed rate equations make reasonable predictions. Batch reactor models initially contained a solution spiked with CO2. These models showed relatively rapid CO2 consumption followed by cessation of the reaction with the glassy and crystalline basalt after the CO2 was exhausted and a terminal pH near eight. The composite basalt model was less successful because the plagioclase continued to react after the CO2 was exhausted causing the pH to rise to an unreasonably high value near 12. Semibatch reactor models containing a solution continuously supplied with CO2 showed relatively rapid CO2 consumption until all basalt was consumed. Complete semibatch reaction produced a sodium and bicarbonate rich solution with a pH near eight for all three basalt compositions.

Vanadium(III)/Vanadium(II) and Hydrogen Evolution Thermodynamic Behavior at the Negative of the All-Vanadium Redox Flow Batteries

The major negative reaction in all vanadium redox flow batteries (VRFBs) is oxidation-reduction reaction of V3+/V2+ couple, while the side reaction is hydrogen evolution reaction (HER). This work demonstrates a method to determine the reaction priority of V3+ reduction and HER occurring at the negative graphite electrode by using steady state polarization curve. The result shows that the reaction priority of V3+ reduction and HER has a strong influence on the state of charge(SoC), hydrogen ion activity and density of charging current. Under the constant charging current density, the method can be concluded the priority reaction occurred at the negative electrode under a given SoC and concentration of proton.

Stability of Epidoxorubicin Hydrochloride in Aqueous Solutions: Experimental and Theoretical Studies

The first-order degradation kinetics of epidoxorubicin were investigated as a function of pH, temperature, and buffers concentrations. The degradation was followed by HPLC. Buffer catalysis was observed in acetate and phosphate buffers. The pH-rate profiles were obtained at 333, 343, 353, and 363 K. The pH-rate expression was kpH=k1×aH+×f1+k2×f1+k3×f2+(k4×f2+k5×f3)×aOH-, where k1, k4, and k5 are the second-order rate constants (mol−1 L s−1) for hydrogen ion activity and for hydroxyl ion activity, respectively, and k2 and k3 are the first-order constants (s−1) for spontaneous reaction under the influence of water. Epidoxorubicin demonstrates the greatest stability in the pH range 3–5. The electrostatic molecular potential orbitals HOMO-LUMO were also defined in order to determine the cause of the reactivity of particular epidoxorubicin molecule domains in solutions with various pH values.

Investigation of Metrological Characteristics of Silver–Silver Chloride Electrodes of GET 54-2011, the State Primary Standard for the pH Activity of Hydrogen Ions in Aqueous Solutions

The technique of manufacturing silver–silver chloride electrodes and the method of their subsequent selection for the State Primary Standard of pH activity of hydrogen ions in aqueous solutions are described.

Commentary: The Spinal Cord Has an Intrinsic System for the Control of pH.

Most physiological processes are sensitive to pH (i.e., hydrogen ion activity) and regulation of pH within tissues and body fluids represents a fundamental homeostatic process in living organisms. At the organismal level, acid-base balance is achieved by fast respiratory modulations of the partial pressure of CO2 in combination with slower transepithelial ion movements to accommodate excretion and retention of bicarbonate and protons in response to acid-base disturbances. At the cellular and subcellular levels, acid-base balance is achieved by ion exchange.

Interfacial Electrostatic Properties of Hydrated Mesoporous and Nanostructured Alumina Powders by Spin Labeling EPR.

Acid-base equilibria and interfacial electrostatic properties of hydrated mesoporous and nanostructured alumina powders are determining factors for the use of these materials in heterogeneous catalysis and as a sorption media for filtration and chromatographic applications including life sciences. Here spin probe electron paramagnetic resonance spectroscopy of pH-sensitive nitroxides was employed to evaluate the surface charge and interfacial acid-base equilibria at the pore surface of mesoporous powders of α-Al2O3, γ-Al2O3, Al2O3 × nH2O, and basic γ-Al2O3 and nanostructured Al2O3 in the form of pristine materials and modified with aluminum-tri-sec-butoxide, hydroxyaluminum glycerate, and several phospholipids. A new pH-sensitive nitroxide probe, 4-dimethylamino-5,5-dimethyl-2-(4-(chloromethyl)phenyl)-2-ethyl-2,5-dihydro-1H-imidazol-1-oxyl hydrochloride semihydrate (nitroxide R1), has been synthesized and characterized. It was found that conditions of preparation of alumina powders exert strikingly large effects on the apparent pK a of nitroxides measured from electron paramagnetic resonance titration curves. Specifically, while the electron paramagnetic resonance titrations curves for the nitroxide R1 in mesoporous powders prepared from basic γ-Al2O3 and Al2O3 × nH2O were shifted by ΔpK a≈ +0.6 and up to ≈ +1.2 pH units respectively, the shift for γ-Al2O3 was found to be much higher: ΔpK a = +3.5. Assuming approximately the same ∆pH = 0.5-1.0 arising from a difference in the hydrogen ion activity between the bulk solution phase and that in a confined pore volume, the samples were ranked in the following order of descending magnitude of the effective surface electrostatic potential Ψ: mesoporous γ-Al2O3 > Al2O3 × nH2O > basic γ-Al2O3 > α-Al2O3. Conditions of the Al2O3 synthesis as well as the surface modification procedures were found to have profound effects on the interfacial electrostatic properties of hydrated samples that are likely related to the nature and concentration of the active sites on the alumina surfaces.

Rate equations for sodium catalyzed amorphous silica dissolution

Newly measured amorphous silica dissolution rate data were combined with data from the literature to produce an equation that predicts the dissolution flux (J, mol/m2s) of amorphous silica as a function of temperature (T, K), sodium concentration (mNa+, molal), and hydrogen ion activity (aH+).J=14.6210-774002.303R1T+8.9510-777002.303R1TmNa+0.490aH+0.377The same data fit equally well to an equation that expresses the dissolution flux as a function of temperature, sodium concentration, and hydroxide ion activity (aOH−).J=14.6210-774002.303R1T+1.73×10610-777002.303R1TmNa+0.490aOH-0.377These equations have the same form as those for quartz (Rimstidt, 2015) and show that sodium ions have the same catalytic effect on amorphous silica dissolution as they do for quartz.

Factors and Predictions for Cadmium Transfer from Soils into Tomato Plants

ABSTRACTSoil-plant transfer models are needed to predict levels of cadmium (Cd) in vegetables when evaluating the food chain risks of Cd contamination in agricultural soils. In the present study, the transfer of Cd from a wide range of soils into tomato plants was investigated in order to identify the major factors and to develop predictive models. It was found that soil pH was the main factor controlling Cd uptake and lower pH was more favorable for Cd bioaccumulation. Furthermore, the hydrogen ion activity, other than pH, was correlated linearly with the ratio of plant Cd to soil Cd. Combining soil Cd, and the interaction between soil Cd and hydrogen ion activity greatly improved the model to predict the transfer of Cd from soil to plant. Compared with the previous log transformation model, the predicted model improved the regression coefficient from 0.799 to 0.973 and has important significance in practice.

Ионно-молекулярная модель памяти. Ассоциативная и эмоциональная память и производство информации в системе памяти

In the article the research object is an associative and emotional memory, as well as the extreme importance of the question of the production of information in the system memory. These kinds of memory are category specific and peculiar. With regard to the production of information in the system memory, the question is about the completion of the memory by memory means. An associative or mechanically-associative memory is the remembering of the fact, which isn’t a target designation of the search, but the essence is a random access to information. You can (and should) be separate from the associative memory the emotional memory: an affective memory, the memory of the senses, is considered as a special kind of memory, although the mechanisms of its occurrence and the implementation don’t have a particularly fundamental difference from the mechanisms of an associative memory. The definition of &amp;#34;a special kind of memory” is fair in the sense that it is a memory exclusively on mood, emotions, experiences, etc. In the case of an emotional memory, only the associations are carried out on an emotional level. But it is necessary to repeated exposure to irritants, contributing to the primary emergence of emotional states, as for associative and emotional memory. Psycho-emotional sphere doesn’t exist apart from the other events taking place in the organism and “is not controlled” by certain molecules and ions. It is obvious that at emotional arousal there is a change in the activity of hydrogen ions, which contributes to the implementation of emotional memory.

PH-Dependent Changes in the Mechanisms of Transport of Chlorine e6 and Its Derivatives in the Blood.

We studied the effects of medium pH on steady-state distribution of chlorine e6 and its derivatives between the main transport proteins of human blood plasma. The decrease in medium pH from weakly alkaline (pH 7.4) to acid (pH 5.0) was followed by an increase in relative affinity of chlorines to lipoproteins and reduced their affinity to serum albumin. pH-Dependent changes in the parameters of distribution of photosensitizers between the plasma and blood cells was revealed. We discussed the role of charge and polarity degree of photosensitizer molecule in the mechanism of binding to serum albumin. A possible role of changes in hydrogen ion activity in the processes of selective accumulation of chlorines by tumor cells is discussed.

Influence of pH and temperature on alunite dissolution: Rates, products and insights on mechanisms from atomistic simulation

The processes, rates, controlling factors and products of alunite (KAl3(SO4)2(OH)6) dissolution were assessed using batch dissolution experiments at pHs of c. 3, 4, 4.6, 7 and 8, and temperatures of c. 280, 293 and 313K. Alunite dissolution is roughly congruent at pH3, while at pH≥3.9 the process is incongruent, giving a lower Al/K ratio in solution than in the pristine alunite sample. The decrease in the Al/K ratio appears to be caused by precipitation of secondary aluminium sulfate/hydroxysulfate minerals coating the surface of the dissolving alunite, as inferred from SEM images and XPS determinations, but these minerals do not passivate the alunite surface for the time frame of the experiments (up to 400h). The lowest dissolution rates are obtained for pH4.6 and 280K. Both the temperature increase and any pH variation from that point lead to faster dissolution rates.Based on the potassium release to solution, the influence of pH and temperature on the alunite dissolution rate for pH of 4.8 and below can be expressed as;rateK=10-4.4±0.5aH+0.10±0.02e-32±3/RTwhere rateK is the alunite dissolution rate (in mol·m−2·s−1); aH+ is the activity of hydrogen ions in solution; R is the Universal gas constant (in kJ·mol−1·K−1) and T is temperature (in K).For pH of 4.6 and above, the alunite dissolution rate can instead be expressed as;rateK=10-2.5±0.8aOH-0.14±0.02e-39±4/RTwhere aOH- is the activity of hydroxyl ions in solution.In light of the calculated values for the activation energy under the two sets of pH conditions (32±3 and 39±4kJ·mol−1), alunite dissolution appears to be surface-controlled. Examination of the most stable solvated alunite surfaces obtained by atomistic computer simulations suggests that the least energetically favourable steps during alunite dissolution are the detachment of either Al atoms or SO4 tetrahedra from exposed surfaces. Thus, these processes are most probably the rate-determining steps in alunite dissolution.

Evaluation of the Deacetylation Degree of Chitosan with Two‐Abrupt‐Change Coulometric Titration

AbstractThe two‐abrupt‐change coulometric titration was proposed for the analysis of the degree of deacetylation of chitosan. The potential was indicated by an antimony electrode which could sensitively response to the variation of activity of hydrogen ion in the turbid and viscous chitosan solution. Through this new approach, the deficiency of combination pH glass electrode in that medium is successfully overcome. The degree of deacetylation of chitosan was obtained by the difference of electrolysis time between two inflection points in the electrolysis process. The measurement error, which is caused by the residual acid or alkali in the chitosan, could be eliminated. The degree of deacetylation of four chitosan samples were investigated by this new method, which found to be consist with those determined by proton nuclear magnetic resonance (1H NMR). The standard deviations were found to be lower than 0.60 % and the whole experimental process can be completed within 15 min. With merit of simplicity, convenience, quickness, accuracy, the proposed new method would possess extensive practicability in scientific research and industrial production.

Rate equations for sodium catalyzed quartz dissolution

Quartz dissolution rate data were fit to an equation that predicts the dissolution flux (J, mol/m2sec) as a function of temperature (T, K), sodium concentration (mNa+, molal), and hydrogen ion activity (aH+). J=0.64610-748002.303R1T+6.6410-880002.303R1TmNa+0.331aH+0.441The same data fit equally well to an equation that expresses the rate as a function of temperature, sodium concentration, and hydroxide ion activity (aOH-). J=0.64610-748002.303R1T+1120010-716002.303R1TmNa+0.326aOH-0.441These equations are more convenient to use than those given by Bickmore et al. (2008) because rates can be predicted without the implementation of a surface speciation model. They predict that at 25°C quartz dissolves more than 200 times faster in seawater than in pure water.These two equations fit the data just as well as five other equations from Bickmore et al. (2008) that are based on surface species concentrations. All of these rate equations contain information about the reaction mechanism(s) for quartz dissolution but that information is ambiguous because the independent variables used to develop the equations are correlated. This means that rate equations alone cannot be used to infer the dissolution mechanism. Existing surface complexation, surface charge, terrace-ledge-kink, and Lewis acid-base models must be modified and amalgamated in order to develop a reliable model of the reaction mechanism(s).

Experimental study of dissolution rates of actinolite in CaCl2–HCl–H2O up to 400 °C

Actinolite dissolution rates in aqueous HCl and aqueous CaCl2–HCl have been measured at temperatures ranging from 25 to 400°C at 23MPa, under conditions far from equilibrium, using a flow-through reactor. The relative release rates for the various elements in actinolite due to breaking of metal–oxygen bonds are all different. All of the release rates vary with temperature and pH. The release rate of Si increases as temperature rises from 20 to 300°C, but then decreases at higher temperatures. Other metallic ions, such as Ca, Mg, Fe, and Al, are all released more rapidly than Si at temperatures between 25 and 300°C, but more slowly at temperatures ⩾300°C. The ratios of mCa/mSi and mMg/mSi in the effluent at 200°C are close to the stoichiometric proportions of these elements in actinolite, but differ from stoichiometric values at temperatures both above and below 200°C. Actinolite dissolution in aqueous HCl at 100°C yields element ratios close to stoichiometric values in the mineral, but again the ratios vary at higher and lower temperatures.Our experiments demonstrate that, under conditions far from equilibrium, dissolution rates depend on both pH and the activity of aqueous MiZi+, where Zi is the valence of the metal Mi in the mineral and MiZi+ refers to Ca2+, Mg2+, or Al3+. The ion-exchange model suggests that metal–hydrogen ion exchange reaction on the surface is a key step for mineral dissolution, and that a Si-rich, Mi-deficient precursor complex is formed on the mineral surface at temperatures <300°C. Using our experimental data, we express the release rate of Si (r) as follows:-r+=Aexp(-EA/RT)((aH+)Zi/aMiZi+)αwhere α is the order with respect to the ratio of activity of hydrogen ions and dissolved metal ions Mi. The Mg–H exchange coefficient, α, is 0.55 at 100°C. The apparent activation energy EA=14.4kJ/mol, and A=0.23×10−3mcm−2s−1.Our results show that water properties vary strongly within the critical region, which affects the dissolution mechanism. Thus, the release rates for various elements at temperatures above 300°C are different from those at temperatures below 300°C. High resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) studies indicate that a Fe(Al)-rich, Si-deficient layer is formed on the surface at temperatures above 300°C. X-ray photoelectron spectroscopy (XPS) analyses show that the surface layer that formed by reaction with aqueous HCl at 400°C is a hydrated silicate, composed of Si–OH and Mi–OH, as well as Si–O and Mi–O bonds.

Ионно-молекулярная модель памяти. Причины, приводящие к искажению информации, хранящейся в памяти

. As in perception, transmission, processing and storage of information in technical systems, distortion (useful) information in the functioning of memory is real and ontologically grounded. The reason of the distortion is the theme of this article from the cycle of works on creation of ion-molecular memory model. By analogy with radio-physical systems – nature is &amp;#34;stingy&amp;#34; on the system moves - the principle of evolutionary conservatism (by I.G. Gerasimov and A. A. Yashin) – the main reason of distortion is an information noise. Classification of information noise in the functioning of memory is developed. The cellular level of noisiness is highlighted. It is shown that an important reason for the distortion of information is a copy of information that is essential for brain function. The repair mechanisms distorted information by modifying the parameters of the spectrum of activity of hydrogen ions are considered. It is important to visualize: informational noise depends on the quality of the information signal, and on the quality of (generalized) receiver of useful information that we observe in the memory structure of the bio-object, in human – in the first place. The evolutionary principle of conservatism, the essence of the system-wide law of the universe, according to which the nature is «stingy» in terms of variety of moves and is based on the famous Poincare hypothesis, now – on the Poincare-Perelman theorem. According to this principle, there is a perfect analogy in the implementation of living and non-living systems, including technical solutions created by man. The prerogative of the cellular level of degradation is even more very obvious: in any system, its qualitative characteristics are determined by the degree of perfection / imperfection of its constituent elements-&amp;#34;primary sources&amp;#34;.

Adair-based hemoglobin equilibrium with oxygen, carbon dioxide and hydrogen ion activity

As has been known for over a century, oxygen binding onto hemoglobin is influenced by the activity of hydrogen ions (H+), as well as the concentration of carbon dioxide (CO2). As is also known, the binding of both CO2 and H+ on terminal valine-1 residues is competitive. One-parametric situations of these hemoglobin equilibria at specific levels of H+, O2 or CO2 are also well described. However, we think interpolating or extrapolating this knowledge into an ‘empirical’ function of three independent variables has not yet been completely satisfactory. We present a model that integrates three orthogonal views of hemoglobin oxygenation, titration, and carbamination at different temperatures. The model is based only on chemical principles, Adair's oxygenation steps and Van't Hoff equation of temperature dependences. Our model fits the measurements of the Haldane coefficient and CO2 hemoglobin saturation. It also fits the oxygen dissociation curve influenced by simultaneous changes in H+, CO2 and O2, which makes it a strong candidate for integration into more complex models of blood acid-base with gas transport, where any combination of mentioned substances can appear.

Water Quality of Fox Sagar Lake, Hyderabad, Telangana State, India, Its Suitability for Irrigation Purpose

Water quality indices provide a simple and understandable tool for managers on the quality and possible uses for irrigation water, however an individual quality factor alone is not enough to evaluate the irrigation water quality because it could be restrictive and sometimes it could give an unfavorable qualification. The aim of this paper is to assess water quality and its suitability for irrigation purpose of Fox Sagar Lake, Hyderabad, Telangana State. As a part of this, fourteen samples were collected from the lake during monsoon season of 2014 and analyzed for various physico-chemical parameters like pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Carbonates (CO3 2- ), Bicarbonates (HCO3 - ), Total Alkalinity (TA), Chloride (Cl- ), Sodium (Na+ ), Potassium (K+ ), Calcium (Ca2+) and Magnesium (Mg2+) were analyzed. To assess the suitability of lake water for irrigation, various indices like Hydrogen Ion Activity (pH), Salinity Hazard, Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Scott quality factor (alkali-metric coefficient or K), Permeability Index (PI) and Kelly's Index (KI) were calculated and found that lake waters falls under good quality

Ионно-молекулярная модель памяти. Формирование информационного пространства памяти посредством ионов водорода

Regular publications on the development of ion-molecular memory model focuses on the development of information area of memory. As in the previous paper, the main active agents are hydrogen ions. Formation of information code is regarded as the effectiveness of the range of activity of hydrogen ions (SAHI). Spectrum of activity is considered as dominant in the organization of transfer processes, storage and conversion information in developed model of memory. According to the position of modern knowledge the diagram of a hypothetical way to the library memory was developed and justified. The authors noted that the possibility of formation of an information code by means of SAHI is physical-logically consistent within the complex logic A.A. Zinoviev as the most perfect in the real time logic device. There is no need to ask the question: why dominates the spectrum of hydrogen? - This chemical is vital in the evolution of the bioorganic world. Supplemental approval is given in the paper, - the possibility of information duality of SAHI show a clear analogy between the latter and DNA. The above is illustrated in this paper as general physical and biophysical arguments and detailed mathematical analysis and thermodynamic description of SAHI. In general, it can be assumed that the proposed model of formation of the information space in memory by means of hydrogen ions carries the actual quality of the adequacy and in private provisions don’t contrary to popular works.