Heterogeneous and homogeneous electron transfer in ambient temperature 1-alkylpyridinium chloride—aluminium chloride melts

1:2 molar ratio 1-methylpyridinium chloride—aluminium chloride and 1:2 m/o 1-butylpyridinium chloride—aluminium chloride melts offer a suitable solvent/supporting electrolyte medium for electrochemical studies of organic as well as inorganic solutes. Novel radical cation formation due to homogeneous electron transfer has also been observed for aromatic compounds having an oxidation potential more negative than + 1.5 V vs sce. Formation of the radical cations via homogeneous electron transfer has been confirmed by electrochemical, uv-vis spectroscopic, and esr techniques. The cation formation depends on the melt acidity, ie the 1-alkylpyridinium chloride—aluminium chloride ratio. These observations indicate that the 1:2 molar ratio 1-alkylpyridinium chloride—aluminium chloride melts are far more acidic than the corresponding 1:2 m/o alkali halide—aluminium chloride fused salt systems.     

Configurational characteristics of ethylene-vinyl chloride copolymers

Rotational isomeric state theory has been used to calculate mean-square unperturbed dimensions 〈r²〉 and dipole moments 〈μ²〉 of ethylene-vinyl chloride copolymers as a function of chemical composition, chemical sequence distribution, and stereochemical composition of the vinyl chloride sequences. As was previously found for several other copolymeric chains, 〈μ²〉 is much more sensitive to chemical composition and chemical sequence distribution than is 〈r²〉₀. The present calculations also indicate that both 〈r²〉₀ and 〈μ²〉 are most strongly dependent on chemical sequence distribution for ethylene-vinyl chloride chains having vinyl chloride sequences which are significantly syndiotactic in structure. In the case of ethylene-vinyl chloride copolymers in which the chemical sequences are relatively short and the vinyl chloride sequences are significantly isotactic, both 〈r²〉₀ and 〈μ²〉 depend on chemical composition in an unexpectedly complex manner; under the cited conditions both of these statistical properties display a maximum and minimum in their variation with chemical composition.     

The apparent and effective chloride migration coefficients obtained in migration tests

The apparent (D_app) and effective (D_eff) migration coefficients obtained in chloride migration tests are investigated in this study. The presented D_app profiles in concrete show that the apparent migration coefficient is strongly concentration-dependent. As demonstrated, the binding of chlorides during the migration tests is very low at low free-chloride concentrations and therefore the chloride penetration front progresses throughout the concrete only slightly retarded by the binding. The diffusion flux during migration tests is shown to be insignificant compared to the migration flux. The D_RCM obtained from the Rapid Chloride Migration (RCM) tests are found to be equal to the computed D_app at the locations of the chloride penetration fronts, which gives an indication that the D_RCM represents only the migration coefficient at the front. A linear correlation is found between the D_RCM obtained from the traditional RCM model and the D_eff obtained from the chloride transport model which includes non-linear chloride binding and concentrations in non-equilibrium.     

The effect of Cu-rich sub-layer on the increased corrosion resistance of Cu-xZn alloys in chloride containing borate buffer

The electrochemical behaviour of Cu-xZn alloys, as well as their constituent metals, in a borate buffer containing chloride ions in the molar range from 0.01 to 1 M are studied. Characteristics of these materials under anodic polarization are compared and the composition and morphology of the corrosion products formed in the course of polarization experiment are analysed by SEM and EDS. X-ray photoelectron spectroscopy and electrochemical impedance measurements are used for characterization of the surface layers formed on Cu, Zn and Cu-40Zn alloy during 2-h immersion at E_oc in a borate buffer containing two different concentrations of chloride ions. New aspects of the behaviour of brass under E_oc condition are revealed. The improved corrosion resistance of brass in chloride media, if compared to zinc metal, is attributed to a Cu-rich layer formed by the selective dissolution of zinc. Based on the results, a structural model describing the improved corrosion resistance of Cu-40Zn alloy with respect to Zn metal is proposed.     

Application of a thermochemical method for studying a low-temperature polycondensation process

A thermochemical method has been used for investigating the course of a polycondensation process. Measurements were performed in a Calvet-type calorimeter. The reactions of triethylamine complex formation with bisphenols and terephthaloyl chloride were investigated. Both hydroxyl groups in the bisphenols are found to be equally reactive with triethylamine. Stability constants, rate constants, and the ΔH⁰, ΔG⁰ and ΔS⁰ values for the reaction of triethylamine with hydroxyl groups were determined. The acid chloride groups in the terephthaloyl chloride are found to exhibit different reactivities with triethylamine. Thermal effects on the reaction of these groups were determined. Results of the measurements are also presented in the form of thermokinetic curves. Such curves obtained for the polycondensation process were compared with those determined for reactions involving the formation of the complex of triethylamine with each of the monomers separately. A mechanism of the polycondensation process is proposed.     

Conductivities of calcium chloride and calcium chloride-sodium chloride solutions saturated in calcium carbide and unsaturated in calcium oxide

The specific conductivity variation of the named solutions vs temperature in the range 750–950°C and vs the sodium chloride molar fractions have been measured. The specific conductivity increases sharply with increasing sodium chloride M fraction and reaches a maximum when the M fraction ratio of sodium chloride to calcium carbide is nearly two. This experimental result has been interpreted by assuming interactions between calcium carbide and sodium chloride, and constitutes a verification of a previous thermodynamic result obtained by the same authors.     

Chlorine evolution reaction on platinum and several alloys

The chlorine evolution reaction on platinum and several alloys was studied by galvanostatic polarization measurements. Linear relationships are found between logarithmic current density, the electrode potential and the coverage of oxide, through the d-band vacancy in the electrode. Logarithmic exchange current density can be related to the dissociation energy of chloride, while any other significant relationships could not be found in its plots against % d-character or the work function. This result suggests that the dissociation energy of chloride plays an important part of chlorine evolution reaction.     

Synthesis, characterization and thermal properties of soluble aromatic poly(amide imide)s

Novel diamines such as N,N′-bis(aminoaryl)terephthalamido-2-carboxylic acids (BATCA), which contain primary amine, amide and carboxylic acid groups and are soluble in dilute aqueous NaOH solution, were synthesized by reacting aromatic diamines with trimellitic anhydride chloride in dimethylformamide. Poly(amide imide)s containing 3:1 ratio of amide:imide groups in the polymer chain were prepared by low temperature solution polymerization of BATCAs with isophthaloyl chloride or terephthaloyl chloride in dimethylformamide at 5-10 °C to form poly(amide amic acid)s, and followed by treating with a mixture of triethylamine and acetic anhydride. The PAIs were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethylsulphoxide and N-methylpyrrolidone, and have inherent viscosities in the range of 0.30-0.66 dL/g. The PAIs were characterized by IR, ¹H NMR and ¹³C NMR techniques. Thermogravimetric analysis (TGA) has shown that the initial decomposition temperatures of the polymers are in the range of 250-440 °C, depending upon the structures of diamine and diacid chloride. The glass transition temperatures of the PAIs are in the range of 128-320 °C. The IDT and T_g values of the polymers containing terephthaloyl unit are higher by about 20-40 °C than those of the polymers with isophthaloyl unit. BATCA could be utilized for the preparation of thin film composite membranes having PAA/PAI barrier layer on PES by in situ interfacial polymerization with IPC/TPC/TMC.     

Correlation of the Rates of Solvolysis of Two Arenesulfonyl Chlorides and of trans-��-Styrenesulfonyl Chloride �C Precursors in the Development of New Pharmaceuticals

Additional specific rates of solvolysis have been determined, mainly in fluoroalcohol containing solvents, for benzenesulfonyl chloride (1) and p-nitrobenzene-sulfonyl chloride (2). For trans-β-styrenesulfonyl chloride (3), a study has been carried out in 43 pure and binary solvents, covering a wide range of hyroxylic solvent systems. For the specific rates of solvolyses of each of the three substrates, a good correlation was obtained over the full range of solvents when the extended Grunwald-Winstein equation was applied. The sensitivities to changes in solvent nucleophilicity and solvent ionizing power are similar to values determined earlier and an S_N2 process is proposed. For 3, kinetic solvent isotope effects of 1.46 for k_H2O/k_D2O and 1.76 for k_MeOH/k_MeOD were determined. These are also compared to literature values for other sulfonyl chlorides.     

FT i.r. and thermal analysis studies of blends of poly(ε-caprolactone) with homo- and copolymers of poly(vinylidene chloride)

FTi.r. and thermal analysis studies have been performed on blends of poly(ε-caprolactone) (PCL) with vinylidene chloride copolymers containing the comonomers vinyl chloride and acrylonitrile. The results indicate that the blends are compatible over the whole composition range in the amorphous state. Attempts were also made to obtain coherent blends of PCL and the homopolymer of vinylidene chloride. Evidence for the presence of specific intermolecular interactions has been obtained and the origin of these interactions is discussed.     

Laboratory RO and NF processes fouling investigation by residence time distribution curves examination

The fouling phenomena of nanofiltration of calcium sulfate saturated feed solution in the presence of magnesium and carbonates as well as the reverse osmosis of saturated silica feedwater with magnesium chloride content at different pH levels, was investigated by analyzing the membrane residence time distribution curves (RTD) in our laboratory. The fraction of degraded membrane (parameter a), the fraction of active membrane area (parameter b) and the fraction of membrane blocked by impermeable layer (parameter c) as a function of permeate recovery was determined. It was found that not only surface blockage affects permeate efficiency, but also other factors, such as module retentate chamber pressure drop and osmotic pressure increase. The membranes RTD measurements as well as fouling, a, b and c parameters, gathered with ion-selective electrodes (chloride, calcium and cupric ion-selective) and appropriate tracer solutions (sodium chloride, calcium chloride and cupric nitrate) were compared with commonly used conductivity sensor and sodium chloride tracer solution. We found that both the tracer and detector type strongly affects membrane mean residence time and its variance, but at the same time no influence of detector and tracer type on membrane fouling a, b and c parameters was observed.     

Effects of chloride ions on hydrothermal synthesis of tetragonal BaTiO3 by microwave heating and conventional heating

Effects of the chloride ions on the synthesis of tetragonal BaTiO₃ in the microwave-hydrothermal (MH) and conventional hydrothermal (CH) processes were investigated. Such effects were found to be dependent of the synthesis method and temperature. In the MH process performed at 240 °C, tetragonal BaTiO₃ powders of c/a ratios larger than 1.009 were readily prepared whether the chloride ions were present or not. At the lower temperature of 220 °C, however, the c/a ratio in the MH BaTiO₃ was only 1.0061 in the absence of the chloride ions but increased to 1.0084 aided by the chloride ions. In the CH process, the chloride ions were observed to play an invariably important role in the preparation of tetragonal BaTiO₃. In contrast, the chloride ions appeared to have less influence on the particle size of the hydrothermal BaTiO₃ in a relatively short period of time.     

Characteristic service life for concrete exposed to marine environments

A statistical treatment has been applied to a deterministic service life model of concrete structures in marine environments. The chloride ingress model based on Fick's second law of diffusion was assumed. The quality of concrete was quantified in terms of three factors, namely, an apparent diffusion coefficient at 1 year (D_a), surface chloride concentration (C_s) and a critical chloride level (C_cr). The standard deviation of service life can be estimated from standard deviations of the four factors, namely, C_s, D_a, C_cr and cover depth. The effect of the severity of environment on service life was also demonstrated. With data from the literature and an approximation of the inverse error function, sensitivity analyses were carried out. Service life was found to be more sensitive to cover depth than the diffusion coefficient, and more sensitive to surface chloride concentration than the critical chloride level. Characteristic service life of a range of normal Portland cement (NPC) concrete grades was evaluated as a function of 28-day strength and cover depths for a nominated confidence level. Such characteristic service life can be readily used and appreciated by design engineers.     

Investigation of the compatibility of butadiene—acrylonitrile copolymers with poly(vinyl chloride)

Various methods were used to study the compatibility of butadiene-acrylonitrile copolymers with poly(vinyl chloride). These blends were investigated by phase contrast microscopy, differential scanning calorimetry and torsion pendulum analysis. We conclude that the copolymers are compatible with poly(vinyl chloride) in all PVC compositions within the range 23–45% acrylonitrile. These blends exhibit a single T_g in the torsion pendulum studies and differential scanning calorimetry studies and follow a Fox expression in the variation of T_g with composition. Experimental densities are also higher than those calculated assuming volume additivity, implying better packing and a negative heat of mixing leading to molecular compatibility.     

Chloride selective potentiometric sensor based on a newly synthesized hydrogen bonding anion receptor

A new potentiometric chloride sensor based on the use of anion receptor 2-(1-H-imidazo [4,5-f][1,10]phenanthroline-2-yl)-6methoxyphenol (HIPM) in poly(vinyl chloride) (PVC) matrix is reported. Effect of various plasticizers: 2-nitrophenyloctylether (o-NPOE), di-n-butylphthalate (DBP), diethyl phthalate (DEP), dioctylpthalate (DOP), tri-n-butyl phosphates (TBP), chloronapthalene (CN) and cation excluder, cetryltrimethylammoniumbromide (CTAB) was studied. The best performance was obtained with a membrane composition of PVC: o-NPOE:HIPM: CTAB ratio (w/w, %) of 31:60:7:3. The sensor exhibits significantly enhanced selectivity towards chloride over the concentration range 5.0 × 10⁻⁸ to 1.0 × 10⁻¹ M with a lower detection limit of 1.0 × 10⁻⁸ M and a Nernstian slope of 59.8 mV decade⁻¹ of activity. Influence of the membrane composition and possible interfering ions was investigated on the response properties of the electrode. Fast and stable response, good reproducibility and long-term stability are demonstrated. The sensor shows response time of <10 s and can be used for about 3 months without any considerable divergence in their potential response. Selectivity coefficients determined with matched potential method (MPM) indicate high selectivity for chloride. The proposed electrode shows fairly good discrimination of chloride from anions. It was successfully applied to determination of chloride ion in packed drinking water. The electrode can be used in the pH range of 6.5-8.0 and mixtures containing up to 20% (v/v) non-aqueous content. It was used as an indicator electrode in potentiometric titration of chloride ion against silver nitrate.     

Powder mixing in a horizontal batch mixer

The mixing process in a horizontal batch mixer with a twin spiral rotor has been investigated.A mixture of crushed wheat and sodium chloride was mixed in a model mixer. The concentration of sodium chloride in mixture samples was checked as a function of the mixing time and sampling place for various degrees of mixer filling. The sample composition was determined by conductometric determination of sodium chloride in water extracts of the sample. From the values obtained, the mixing degree was calculated as defined by the variation coefficient along the whole mixer, as a function of the mixing time.In analysing the data and empirical correlation between the concentration of component under study and the place and time of mixing, C/C? = f(x, t) was obtained and compared with industrial experiments using radionuclides as tracers.     

Growth kinetics of an indigenous mixed microbial consortium during methylene chloride degradation in a batch reactor

Biodegradation of methylene chloride by a mixed microbial culture, isolated from a common sewage treatment plant, was investigated in a batch system. Batch experiments were performed at room temperature (27 °C) and pH value of 7. The methylene chloride concentration in growth media varied from 25 mgl^?1 to 250mgl^?1. A maximum observed degradation was 1 mgl^?1h^?1 at 100 mgl^?1 of methylene chloride. The culture followed substrate inhibition kinetics and specific growth rate were fitted to different substrate inhibition models (Haldane, Aiba and Edwards models) by MATLAB 7.1@. Among all models, Haldane was found to better fit with root mean square of 0.947. The biokinetic constants estimated using these models show good potential of the mixed microbial culture in methylene Chloride degradation. Escherichia coli and Staphylococcus aureus are predominant microbes present in the mixed culture.     

Synthesis of cationic amphiphilic diblock copolymers of poly(vinylbenzyl triethylammonium chloride) and polystyrene by reverse iodine transfer polymerization (RITP)

A new method called reverse iodine transfer polymerization (RITP), based on the in situ generation of transfer agents using molecular iodine I₂, was applied to the synthesis of poly(vinylbenzyl chloride). Well-defined diblock copolymers poly(vinylbenzyl chloride)-b-polystyrene with different chain lengths were then successfully produced through sequential polymerization of styrene. The polydispersity index values M_w/M_n ranged from 1.4 to 1.6 for all the homopolymers and diblock copolymers. The diblock copolymers could be synthesized with equally good results by starting with either poly(vinylbenzyl chloride) or polystyrene as macrotransfer agents. The diblock copolymers were then quaternized with triethylamine to prepare cationic amphiphilic diblock copolymers.     

Time dependent diffusion in concrete—three laboratory studies

The rate of chloride diffusion into concrete decreases with time due to issues such as continued hydration and chloride binding. Data are presented from three projects where the specimens were continuously exposed to chloride solutions for periods ranging from 28 days to 3 years. Chloride profiles obtained from the specimens at various time intervals were used to calculate diffusion values using Crank's solution to Fick's second law. The time-dependant reduction coefficient, m, was determined using three methods, yielding different values. Since the reduction of calculated diffusion coefficients with time has great impact on service life predictions, and values are sensitive to the method used, it is imperative to also know how the diffusion and time-dependant reduction coefficients were obtained.