Bubble points of hydrogen chloride–water–isopropanol and hydrogen chloride–water–isopropanol–benzene systems and liquid–liquid equilibria of hydrogen chloride–water–benzene and hydrogen chloride–water–isopropanol–benzene systems

Bubble points of the HCl–water–isopropanol and the HCl–water–isopropanol–benzene systems and liquid–liquid equilibria (LLE) of the HCl–water–benzene and the HCl–water– isopropanol–benzene systems were measured at 25–85°C and 30–70°C, respectively. The electrolyte nonrandom two-liquid model proposed by Chen et al. [C.-C. Chen, H.I. Britt, J.F. Boston, L.B. Evans, AIChE J. 28 (1982) 588–596] can satisfactorily correlate bubble points and liquid–liquid equilibria of the present mixed-solvent electrolyte systems over the entire range of temperature and concentrations using only binary adjustable parameters.     

Selective oxidation of sulfides to sulfoxides with cyanuric chloride and urea–hydrogen peroxide adduct

Although a number of methods have been developed for the selective oxidation of sulfides to sulfoxides, the need remains for alternative efficient, reliable strategies that can be generally applied to various sulfides and that use readily available reagents under mild reaction conditions. Herein, we report the use of urea–hydrogen peroxide adduct (UHP) and cyanuric chloride in CH₃CN at room temperature to convert sulfides to sulfoxides in excellent yields. In particular, this protocol produced sulfoxides with aromatic rings bearing electron-withdrawing groups in excellent yields.     

Hydrogen bond CH…O in a methanolic solution of hydrogen chloride

The existence of a hydrogen bond in which a methyl group of the (MeOH)₂H⁺ ion acts as a proton donor is examined. The fundamental vibration frequencies of this ion were calculated for different numbers and strengths of CH…O bonds. The atomic charges in neutral ((MeOH) _n ,n=1–4) and protonated ((MeOH) _m H⁺,m=2–6) associates of methanol molecules were also calculated. The experimentally observed decrease in the v(CH) vibration frequencies of the (MeOH)₂H⁺ ion to 2890 cm⁻¹ and 2760 cm⁻¹ is attributable to the fact that each methyl group of the ion is involved in formation of two CH…O bonds with strength of −12.5 kJ mol⁻¹. The proton-donating ability of the CH bond depends on the charge on its H atom; however, it does not correlate with the dipole moment of this bond. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 306–312, February, 1999.     

Infrared matrix isolation studies of the trimethylamine oxide—hydrogen chloride complex

The reaction products of the codeposition of trimethylamine oxide and a HCl/Ar mixture are characterized by diffuse absorption in the region from 1850 to ca 3200 cm⁻¹ and by a strong band at 1700 cm⁻¹. These absorptions are assigned respectively to the OH⁺...Cl⁻ antisymmetric stretching and in-plane bending modes, which indicates that proton transfer to basic oxygen occurs.     

Hydrogen sorption–desorption studies on ZrCo–hydrogen system

The ZrCo–H₂ system was investigated in this study owing to its importance as a suitable candidate material for storage, supply, and recovery of hydrogen isotopes. Desorption hydrogen pressure-composition isotherms were generated at six different temperatures in the range of 524–624 K. A van’t Hoff plot was constructed using the plateau pressure data of each pressure-composition isotherms and the thermodynamic parameters were calculated for the hydrogen desorption reaction of ZrCo hydride. The enthalpy and entropy change for the desorption of hydrogen were found to be 83.7 ± 3.9 kJ mol^?1 H₂ and 122 ± 4 J mol^?1 H₂ K^?1, respectively. Hydrogen absorption kinetics of ZrCo–H₂ system was studied at four different temperatures in the range of 544–603 K and the activation energy for the absorption of hydrogen by ZrCo was found to be 120 ± 5 kJ mol^?1 H₂ by fitting kinetic data into suitable kinetic model equation.     

Sensor–actuator system for dynamic chloride ion determination

Chloride is a crucial anion for various analytical applications from biological to environmental applications. In order to measure the chloride ion concentration, a measurement system is needed which can detect this concentration for prolonged times reliably. Chronopotentiometry is a technique which does not need a long term stable reference electrode and is therefore very suitable for prolonged ion concentration measurements. As the used electrode might be fouled by reaction products, this work focuses on a chronopotentiometric approach with a separated sensing electrode (sensor) and actuating electrode (actuator). Both actuation and sensor electrode are made of Ag/AgCl. A constant current is applied to the actuator and will start the reaction between Ag and Clˉ, while the resulting Clˉ ion concentration change is observed through the sensor, which is placed close to the actuator. The time it takes to locally deplete the Clˉ ions is called transition time. Experiments were performed to verify the feasibility of this approach. The performed experiments show that the sensor detects the local concentration changes resulting from the current applied to the actuator. A linear relation between the Clˉ ion concentration and the square root of the transition time was observed, just as was predicted by theory. The calibration curves for different chips showed that both a larger sensor and a larger distance between sensor and actuator resulted in a larger time delay between the transition time detected at the actuator and the sensor.     

Electrosynthesis and biological properties of persulfate–chloride solutions

A method for electrochemical synthesis of medical solutions for oxidation of toxic substances in the human organism has been developed. The method is based on electrooxidation of sodium sulfate in the presence of chloride and NaOH microadditions (in amounts that provide рН 13) in a filter-press membrane electrolyzer. A diagram is presented for choosing the optimum ratio between the current density and the flow rate of electrolyte during the electrosynthesis of a medical solution. The use of an electrolyte of the suggested composition under the optimum electrosynthesis conditions leads to solutions with physiological рН values (7.2–7.4) and high oxidative ability with respect to Micrococcus sp. and Staphylococcus coag (–), but there was no injuring effect on blood cells.     

Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

Electrooxidation of hydrogen at Pt/carbon nanotube catalysts for hydrogen–air fuel cell

A possibility for application of the method of thin-layer rotating disk electrode (RDE) for investigation of kinetics of hydrogen electrooxidation on highly dispersed platinum catalysts formed on the carbon nanotubes (CNT) is studied. It is shown that the polarization curves of hydrogen oxidation on the studied catalysts approach the calculated curves for the diffusion overpotential of hydrogen reaction both in the acidic and alkaline electrolytes. This is the evidence, on the one hand, for a high activity of proposed catalysts in the hydrogen oxidation reaction and, on the other hand, for incorrect use of the Koutecky–Levich equation for calculating the kinetic currents in the case under consideration. The characteristics of hydrogen–oxygen fuel cell (FC) with anode based of synthesized 40Pt/CNT catalysts are highly comparative with the characteristics of FC containing commercial 60Pt catalyst (HiSPEC 9100) on the anode.     

The reactions of perfluorinated α- and β-alkoxyradicals with hydrogen chloride, chlorine and fluorine

The kinetics of the reactions of the macroradicals R_f′OCF₂ (I) and R_f′OCF₂CF₂ (II) with HCl, Cl₂ and F₂ have been studied in the liquid phase, being R_f′ a poly(oxydifluoromethylene-oxytetrafluoroethylene) chain with average molecular weight of about 10⁴ Da. Radical (I) showed a higher reactivity compared to radical (II) with all the three radical transfer agents.In case of HCl the activation energy for the reaction:

     

Anomalous codeposition of cobalt and ruthenium from chloride–sulfate baths

Codeposition of Ru and Co was studied at room temperature and at 50 °C with various Ru³⁺ and Co²⁺ concentrations in the electrolyte. The codeposition of Co and Ru proved to be anomalous since no pure Ru could be obtained in the presence of Co²⁺ in the electrolyte, but a significant Co incorporation into the deposit was detected at potentials where the deposition of pure Co was not possible. The composition of the deposits varied monotonously with the change of the concentration ratio of Co²⁺ and Ru³⁺. The deposition of Ru was much hindered, and the current efficiency was a few percent only when the molar fraction of Co in the deposit was low. Continuous deposits could be obtained only when the molar fraction of Co in the deposit was at least 40 at.%. The deposit morphology was related to the molar fraction of Co in the deposit. The X-ray diffractograms are in conformity with a hexagonal close-packed alloy and indicate the formation of nanocrystalline deposits. Two-pulse plating did not lead to a multilayer but to a Co-rich alloy. Magnetoresistance of the samples decreased with increasing Ru content.     

[Phthalocyaninato(2–)]­antimony(III) chloride

The title antimony(III) complex, [Sb(C₃₂H₁₆N₈)]Cl or [SbPc]Cl (where Pc = C₃₂H₁₆N₈²⁻), has been obtained from the reaction of pure powdered antimony with 1,2-di­cyano­benzene under a stream of ICl vapour. The asymmetric unit of this complex consists of an [SbPc]⁺ cation and a Cl⁻ anion. The phthalocyaninate residue [SbPc]⁺ is not planar. The Sb atom lies 1.057 (3) Å from the plane defined by the four iso­indole N atoms. A combination of ionic and donor–acceptor interactions links the [SbPc]Cl mol­ecules to form centrosymmetric [(SbPc)Cl]₂ pseudo-dimers in the crystal. The Sb—Cl distances in the pseudo-dimer are not equivalent [3.043 (2) and 3.201 (2) Å]. The pseudo-dimers are weakly linked through Cl⃛H—C_benzo interactions to form a three-dimensional network. As a result of these interactions, the four Sn—N_isoindole bond lengths in the [SbPc]⁺ residue are not equivalent and the symmetry of the Sb—N core is only close to C_s.     

Comparative characteristics of cathodes with different catalytic systems in hydrogen–oxygen and hydrogen–air fuel cells with proton-conducting polymer electrolyte

The characteristics of low-temperature hydrogen–oxygen (air) fuel cell (FC) with cathodes based on the 50 wt % PtCoCr/C and 40 wt % Pt/CNT catalysts synthesized on XC72 carbon black and carbon nanotubes (CNT) are compared with the characteristics of commercial monoplatinum systems 9100 60 wt % Pt/C and 13100 70% Pt/C HiSPEC. It is shown that the synthesized catalysts exhibit a high mass activity, which is not lower than that of commercial Pt/C catalysts, a high selectivity with respect to the oxygen reduction to water, and a significantly higher stability. The characteristics of PtCoCr/C and Pt/CNT were confirmed by testing in the hydrogen—oxygen FCs. However, when air was used at the cathode, especially in the absence of excessive pressure, a voltage of FC with the cathode based on PtCoCr/XC72 is lower as compared with the commercial systems. Probably, this is associated with the transport limitations in the structure of trimetallic catalyst synthesized on XC72 carbon black due to the absence of mesopores. This drawback was eliminated to a large extent by raising the volume of mesopores as a result of application of mixed support (XC72 + CNT) and the use of only CNT for the synthesis of the monoplatinum catalyst. However, this did not eliminate another drawback, namely, a low platinum utilization coefficient in the cathode active layer as compared with that measured under the model conditions in the 0.5 M Н₂SO₄ solution. Therefore, further research is required to improve the structure of the catalytic systems, which are synthesized both on carbon black and nanotubes, while maintaining their high stability and selectivity.     

Helium–hydrogen microplasma device (MPD) on postage-stamp-size plastic–quartz chips

A new design of a miniaturized, atmospheric-pressure, low-power (e.g., battery-operated), self-igniting, planar-geometry microplasma device (MPD) for use with liquid microsamples is described. The inexpensive MPD was a hybrid, three-substrate quartz–plastic–plastic structure and it was formed on chips with area the size of a small postage stamp. The substrates were chosen for rapid prototyping and for speedy device-geometry testing and evaluation. The ~700-µm (diameter) and 7-mm (long) He–H₂ (3% H₂) microplasma was formed by applying high-voltage ac between two needle electrodes. Operating conditions were found to be critical in sustaining stable microplasma on plastic substrates. Spectral interference from the electrode materials was not observed. A small-size, electrothermal vaporization system was used for introduction of microliter volumes of liquids into the MPD. The microplasma was operated from an inexpensive power supply. And, operation from a 14.4-V battery has been demonstrated. Microplasma background emission in the spectral range between 200 and 850 nm obtained using a portable, fiber-optic spectrometer is reported. Analyte emission from microliter volumes of dilute single-element standard solutions of Cd, Cu, K, Li, Mg, Mn, Na, Pb, and Zn is documented. Element-dependent precision was between 10–25% (the average was 15%) and detection limits ranged between 1.5 and 350 ng. The system was used for the determination of Na in diluted bottled-water samples.     

Vapor–liquid equilibria predictions of hydrogen–hydrocarbon mixtures with the Huron–Vidal mixing rule

An excess Gibbs-equation of state (G^E-EoS) framework based on the Huron–Vidal mixing rule, has been applied to study vapor–liquid equilibria (VLE) of hydrogen–hydrocarbon mixtures. The mixing rule couples the Peng–Robinson–Stryjek–Vera (PRSV) EoS with a local composition solution model. The solution model is based on one-fluid theory treatment and assigns a single energy parameter to each binary pair. This energy parameter relates to the preference of the molecules for like to unlike interactions. The allocation of a system's number of interactions to the individual species in a binary mixture, incorporates the use of size parameters which gain significance only in the liquid phase. In a two parameter form, the framework has been used for the simultaneous data reduction of a large number of binary and several ternary hydrogen–hydrocarbon mixtures. These systems were taken over an extended range of pressures and temperatures. Results from the data reduction are reported in both tabular and graphical forms. Correlations for the model parameters have been identified with the acentric factor of the hydrocarbon in hydrogen–hydrocarbon binary mixtures. In a fully predictive mode, the model has shown to describe well VLE of binary hydrogen–linear alkane systems. Comparisons of these results with calculations from the Peng–Robinson (PR) EoS and the classical mixing rule (vdW) are included.     

Liquid–liquid–solid equilibrium for the water + sodium chloride + potassium chloride + 1-butanol quaternary system at 25 °C

The methodology for the study of the liquid–liquid–solid equilibrium of quaternary systems including two inorganic salts, water and an organic solvent has been reviewed and applied to the water + sodium chloride + potassium chloride + 1-butanol quaternary system at 25 °C. The different equilibrium regions have been systematically studied.The experimental equilibrium data have been used to check the accuracy of the predictions using the electrolyte NRTL model (MNRTL) and the parameters obtained by correlation of ternary systems. The results obtained with the model are satisfactory.     

Nonenzymatic glucose sensing at ruthenium dioxide–poly(vinyl chloride)–Nafion composite electrode

Development of nonenzymatic glucose sensors with high reproducibility and stability is an urgent need to reduce cost of regular diabetic monitoring. Here, we have fabricated ruthenium dioxide–poly(vinyl chloride)–Nafion (RuO₂–PVC–Nafion) composite for direct glucose sensing in sodium hydroxide and phosphate buffer nonenzymatically for the first time. The restricted activity of the RuO₂–PVC film electrode in alkaline pH is extended to neutral pH using Nafion as an outer membrane, which reduces the distance between Ru active sites by bridging effect and improves the electrode stability. The catalytic rate, measured in terms of change of RuO₂ resistance, is similar irrespective of the medium for the high temperature annealed RuO₂ (700 °C), whereas the low temperature annealed RuO₂ (300 °C) is highly sensitive for the change in the pH of the solution. This is revealed by observing large Michaelis–Menten kinetic constant K _M for the RuO₂ (700 °C) than the low temperature annealed RuO₂ (300 °C) due to effective increase in the catalytic active sites similar to oxygen evolution reaction. Contrast to this, the buffer solution does not influence significantly the apparent K _M observed for RuO₂ (300 °C) and has greater impact on the high temperature 500 and 700 °C annealed RuO₂ samples. Cyclic voltammetry, chrono amperommetry, and electrochemical impedance spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques are used for characterization of the sensor behavior. The RuO₂–PVC–Nafion senses glucose selectively in the presence of potential interferences like fructose, galactose, mannose, sucrose, starch, uric acid, ascorbic acid, dopamine, and catechol in NaOH and phosphate buffer. Glucose sensing in the blood serum of the diabetic and nondiabetic patients is made. The results suggest that the RuO₂–PVC–Nafion is a promising candidate for the development of nonenzymatic glucose sensors.