Electrochemical studies of the reaction between titanium metal and titanium ions in the KCl-NaCl molten salt system at 973 K

The reaction between titanium metal and titanium ions in the KCl?NaCl molten salt system was investigated by means of electrochemical and physical methods at 973 K in an inert gas atmosphere (argon). It was found that the reaction between titanium metal and Ti³⁺ in the molten salts with TiCl₃ followed a simple reaction (I). However, in the case of the concentration of K₂ TiF₆ being higher than 2.7 mol % the reaction was (II); in the case of it being less than 0.8 mol %, reactions (III) and (III′) were followed. $$\begin{gathered} 2Ti^{3 + } + Ti = 3Ti^{2 + } (I) \hfill \\ 3Ti^{4 + } + Ti = 4Ti^{3 + } (II) \hfill \\ Ti^{4 + } + Ti = 2Ti^{2 + } (III) \hfill \\ 3Ti^{2 + } = Ti + 2Ti^{3 + } (III')(on cooling) \hfill \\ \end{gathered} $$ It was also found that these reactions were controlled by charge transfer and diffusion simultaneously.     

Experimental determination of the factors affecting zinc electrowinning efficiency

A series of experiments were conducted to investigate the factors affecting the efficiency of zinc electrowinning. The experiments were conducted in 10-1 cells using a high purity industrial zinc sulphate solution. The lowest specific energy consumption achieved in the cells was 2637 kWh t^?1 Zn under the following conditions: $$\begin{gathered} 70 g1^{ - 1} Zn in cell solution \hfill \\ 180 g1^{ - 1} H_2 SO_4 in cell solution \hfill \\ 45^\circ C cell temperature \hfill \\ 400A m^{ - 2} current density \hfill \\ \end{gathered} $$ Further energy savings can be achieved by reducing the current density but this would also reduce the cellroom production capacity. Increasing the electrolyte temperature to 50° C also reduced the energy consumption, however additives capable of controlling deposit morphology at these high temperatures were required. The effects of zinc concentration, acid concentration, deposition time and additive levels are also reported.     

Studies concerning charged nickel hydroxide electrodes. VII. Influence of alkali concentration on anodic peak positions

After repetitive potential cycling employing a high positive potential limit (>700 mV wrt Hg/HgO/ KOH) three anodic and one cathodic peak can be observed using aβ-Ni(OH)₂ starting material. Anodic peaks found at 425, 470 and 555 mV in 5 mol dm^?3 KOH shift to less positive potentials as the alkali concentration is increased appearing at 365, 410 and 455 mV respectively in 12.5 mol dm^?3 KOH. Four anodic processes involving various pairs of coexisting phases within both theβ andα-/γ-phase system can be identified as summarized below in order of increasing positive potential: Peak A $$\begin{gathered} Peak A{\text{ }}U_\alpha ^A \to {\text{ }}V_\gamma ^A \hfill \\ Peak B{\text{ }}U_\beta ^B \to {\text{ }}V_\beta ^B \hfill \\ {\text{ }}\mathop C\limits^ + {\text{ }}U_\alpha ^C \to {\text{ }}V_\gamma ^C \hfill \\ Peak E{\text{ }}V_\beta ^B \to {\text{ }}V_\gamma ^E \hfill \\ \end{gathered} $$ Observed shifts in anodic and cathodic peak potentials are consistent with the known influence of alkali and water activity on the reversible potentials for the above processes.     

The effect of position of ester group on critical micelle concentration of ester-linked sulfonates

The critical micelle concentration (CMC) of sodium alkyl sulfoacetates and β-sulfopropionates, and sodium salt of 2-sulfo ethyl ester, 3-sulfo propyl ester and 4-sulfo butyl ester of fatty acids have been determined by the electrical conductance of each aqueous solution. The relation between CMC value and number of total methylene groups (N) for the C_n ^*H_2n ^*+₁COO(CH₂)₃ SO₃Na and C₉H₁₉COO(CH₂)_n ^**SO₃Na (n^*=9, 10 and 11. n^**=2, 3 and 4) can be formulated as follows. $$\begin{gathered} \log {\text{CMC = - 0}}{\text{.293N + 1}}{\text{.778}} \hfill \\ {\text{for C}}_{\text{n}} *{\text{H}}_{{\text{2n}}} *_{ + ^1 } {\text{COO (CH2) 3SO3Na}} \hfill \\ {\text{log CMC = - 0}}{\text{.147 N + 0}}{\text{.011}} \hfill \\ {\text{for C9H19 COO (CH2) n **SO3Na}} \hfill \\ \end{gathered} $$ From these equations it was determined that the methylene unit situated between ester and sulfonate groups is equivalent to 0.5 methylene groups in its effect on CMC. For a given number of carbon atoms in the alkyl chain, the log CMC value increased regularly with a change in the ester group away from the terminal position to more central positions in the hydrocabon chain. The two different types of ester-linkages (RCOO-and ROCO-) have no apparent effect on the CMC value.     

The thermoelectric power in Bi2O3

The thermo electric power, ΔE/ΔT, of the cell $$\begin{gathered} O_2 + N_{2, } Pt/Bi_2 O_3 (\delta phase)/Pt, O_2 + N_2 \hfill \\ (T + \Delta T) (T) \hfill \\ \end{gathered}$$ has been measured as a function of oxygen pressure (10^?4 atm ? p(O₂) ? 1 atm) in the temperature range 650–800° C. The experimental result can be described by: $$[ \in ({\rm O}_2 /{\rm O}^{2 - } ) - \in (e, Pt)] = [45.6 \pm 5.6 log p(O_2 ) - 261](\mu VK^{ - 1} )$$ within experimental error, where ε(O₂/O²), the Seebeck coefficient ofδ-Bi₂O₃, stands for \(\mathop {\lim }\limits_{\Delta T \to 0} \Delta E/\Delta T\) The change of ΔE/ΔT with oxygen pressure corresponds to the change of the partial molar entropy of O₂. The heat of transport of O^2? ions is calculated to be 0.13 eV ± 0.01 whereas the activation enthalpy for ionic conduction is 0.30 eV. From this discrepancy it is concluded that the free ion model of Rice and Roth cannot be applied, while the extended lattice gas model of Girvin might explain the results when strong polaron coupling is assumed.     

Comparative e.m.f. study of CaF2 and β-alumina cells with Ni/NiF2 and Fe/FeF2 or Cr/CrF2 electrodes

The reliability of employing beta-alumina as electrolyte for fluorine potential measurement is examined by measuring the e.m.f.s of the galvanic cells with metal/metal fluoride electrodes and comparing with those obtained by using CaF₂ as electrolyte under identical conditions. The results from both types of galvanic cell can be superimposed to give the following standard Gibbs energy of formation, ΔG _f ⁰ , of FeF₂ and CrF₂ over extended ranges of temperature: $$\begin{gathered} \Delta G_f^0 (FeF_2 ) = - 702.0 + 0.125 20T (K) ( \pm 0.70) kJ mol^{ - 1} (506 - 1063K) \hfill \\ \Delta G_f^0 (CrF_2 ) = - 732.8 + 0.087 90T (K) ( \pm 0.64) kJ mol^{ - 1} (497 - 1063K) \hfill \\ \end{gathered} $$ The absence of significant temperature-dependent errors in both these measurements are verified by a third law treatment of the data yielding values of ?716.8 and ?777.4 kJ mol^?1 for ΔH _f.298 ⁰ of FeF₂ and CrF₂, respectively. The feasibility of using beta-alumina electrolyte cells for e.m.f. measurements on other metal/metal fluoride systems is discussed in the light of the existence of a useful potential domain of beta-alumina. High sodium potential in the electrode system can lead to sodium depletion. Likewise, low sodium potential may result in oxidation of the metals in the electrodes. Both these limiting factors are also examined.     

Hydrodynamic properties of coal in turbulent fluidized beds

Hydrodynamic properties in turbulent fluidized beds of three different sizes of coal (d _p = 0.507, 0.987, 1.147 mm) have been determined from the pressure fluctuations in a 0.1 m-ID × 3.0 m high Plexiglas column. The transition velocity from the slugging to turbulent flow regimes can be determined from the statistical analysis of pressure fluctuations such as mean amplitude, standard deviation and skewness, the pressure wave velocity, and the bed expansion with gas velocity. The bed expansion in the slugging and turbulent flow regimes cannot be estimated from the two-phase theory. The voids rise velocity and the bed expansion ratio (H/H _mf ) in the turbulent flow regime have been correlated with the relevant dimensionless and operating parameters The ransition velocity to the turbulent flow regime has been determined based on the slug breakdown caused by the inertial force of an upflowing maximum stable slug which overcomes the gravitational force induced by solid refluxing as:      

Electrochemical study of aluminium ion reduction in acidic AlCl3-n-butyl-pyridinium chloride melts

Electrochemical reduction of AlCl₃ dissolved in acidic AlCl₃-n-butyl-pyridinium chloride melt was studied by linear sweep voltammetry and chronopotentiometry at tungsten and platinum electrodes, in the Al₂Cl ₇ ^? concentration range 0.3 to 0.5 M between 30 and 60°C. Al₂Cl ₇ ^? bulk reduction was preceded by a nucleation (tungsten) or alloy formation phenomenon (platinum). The overall results agree rather well with the mechanism: $$\begin{gathered} 2AlCl_4^ - \rightleftarrows Al_2 Cl_7^ - + Cl^ - \hfill \\ 4Al_2 Cl_7^ - + 3e \rightleftarrows Al + 7AlCl_4^ - \hfill \\ \end{gathered} $$ The electrochemical reaction appeared quasi-reversible. Calculated values of the product of the transfer coefficient by the number of the electron exchanged in the rate determining step were in the range 0.45 to 0.7. Diffusion coefficients for Al₂Cl ₇ ^? were calculated.     

The effect of electro-osmosis on the synthesis of lead and tin fluoroborates

Pronounced electro-osmosis phenomena were observed during the anodic dissolution of lead and tin in fluoroboric acid with an anionic exchange membrane separating the anode compartment from the cathode compartment. The consequent volumetric increment of anolyte was influenced by the current density and the initial volume and concentration of catholyte. The selectivities (S _i) of the given membrane were found to be $$\begin{gathered} 50\% Sn(BF_4 )_2 solution: S_{BF^{4 - } } = 0.952; S_{Sn^{2 + } } = 0.048 \hfill \\ 50\% Pb(BF_4 )_2 solution: S_{BF^{4 - } } = 0.887; S_{Pb^{2 + } } = 0.113 \hfill \\\end{gathered}$$      

Characteristic velocity and mass transfer in rotating impeller column

The effects of system variables on flow characteristics and mass transfer rate were studied in a rotating impeller column using a ternary system of water (continuous phase)-acetone (solute)-cyclohexane (dispersed phase). The characteristic velocity, Peclet numbers in both phases and mass transfer coefficient between phases were correlated as; $$\begin{gathered} \bar U_o = 6.3(10^2 )(Nd_I )^{ - 2.1} Z_C^{0.83} \hfill \\ \frac{{\bar U_C L}}{{D_C }} = 1.26N^{ - 1.11} d_I ^{ - 2.17} Z_C^{0.59} \bar F_C^{1.9} \hfill \\ \frac{{\bar U_d L}}{{D_d }} = 20.5N^{ - 0.78} d_I ^{ - 1.36} Z_C^{0.25} \bar F_C^{0.09} \hfill \\ \frac{{k_{OC} aL}}{{\bar U_d }} = 13.2N^{ - 1.33} d_I ^{0.74} Z_C^{0.93} \bar F_C^{0.78} \hfill \\ \end{gathered} $$      

Analysis of commercial anhydrous tetrasodium pyrophosphate

A titration method of analysis is given for Na₄P₂O₇ in commercial anhydrous tetrasodium pyrophosphate using a modification of the Britske and Dragunov titration method. In the absence of other polyphosphates, a degree of precision is obtained satisfactory for the type of product supplied by the manufacturers. Time required for analysis is much less than for methods relying upon precipitation with subsequent gravimetric treatment. Results of cooperative work are given. During 1939 Committee D-12 on Soaps and Other Detergents of A. S. T. M. formulated specifications for tetrasodium pyrophosphate (anhydrous) which now appear as their specification D 595-42 T. The subcommittee on Analysis of Special Detergents was asked to provide a method of analysis of reasonable accuracy for use on commercial material containing about 95 to 100% Na₄P₂O₇. A search of the literature suggested several possible methods (1,2,3) and various modifications supplied by interested laboratories were considered. Cooperative work was carried out by ten laboratories with the result that the following modification of the Britske and Dragunov method (2) was adopted as a Tentative Standard of the A. S. T. M. (4) in 1941 and has just recently been advanced to Standard. The procedure describes an indirect determination of tetrasodium pyrophosphate by titration of the sulfuric acid liberated by the action of zinc sulfate on an acid pyrophosphate in accordance with the following reactions:

$$\begin{gathered} Na_4 P_2 O_7 + 2HCl = Na_2 H_2 P_2 O_7 + 2NaCl \hfill \\ Na_2 H_2 P_2 O_7 + 2ZnSO_4 = Zn_2 P_2 O_7 + Na_2 SO_4 + \hfill \\ H_2 SO_4 \hfill \\ \end{gathered}$$     

Electrical conductivity of low melting baths for aluminium electrolysis: the system Na3AlF6-Li3AlF6- AlF3 and the influence of additions of Al2O3, CaF2, and MgF2

The electrical conductivity was investigated for a section of the molten ternary mixture Na₃AlF₆-Li₃AlF₆-AlF₃ with molar ratio n(Li₃AlF₆):n(AlF₃) = 1 : 2. The conductivity of this system can be described by the following equation: where (i) represent the mole fractions of the additions. The influence of additions of CaF₂, MgF₂ and/or Al₂O₃ on the electrical conductivity of the binary system Na₃AlF₆-Li₃AlF₆ and the ternary system Na₃AlF₆-Li₃AlF₆-AlF₃ was also studied.     

A simple and efficient oxidation system for the oxidation of alcohols utilizing Oxone® as oxidant catalyzed by polymer-supported 2-iodobenzamide

$\begin{array}{l}{\hbox{R}^1\hbox{R}^2\hbox{CHOH}} \\ {\hbox{RCH}_2\hbox{OH} }\end{array} \dynrightarrow{Oxone}{\hbox{CH}_3\hbox{CN/H}_2\hbox{O}, 70^{\circ}\hbox{C}} \begin{array}{l}{\hbox{R}^1\hbox{R}^2\hbox{CO}} \\ {\hbox{RCOOH}} \end{array} A simple and environmentally friendly procedure for the oxidation of alcohols is presented utilizing Oxone^? (2KHSO₅ · KHSO₄ · K₂ SO₄) as oxidant and polymer-supported 2-iodobenzamide as catalyst in CH₃CN/H₂O mixed solvents.     

Electrochemical behaviour of CuO-TiO2 catalysts

In order to provide further information on the properties of CuO?TiO₂ catalysts, we have investigated their electrochemical behaviour in 1 M LiClO₄-propylene carbonate electrolyte. It appears that TiO₂ is electrochemically reducible at 1.8 V at room temperature, with a faradaic yield of 0.3–0.4 F per mole of TiO₂ with formation of a TiO₂Li_x phase according to the reaction: $$TiO_2 + xe + xLi^ + \leftrightharpoons TiO_2 Li_x $$ The electrochemical study suggests that TiO₂ enhances Cu(II) electroreduction in titania-supported copper catalysts. This electroreduction of Cu(II) occurs either at 2.2 V according to the path: $$Cu(II) + 2e \xrightarrow{{TiO_{2 } support}} Cu(O), TiO_2 $$ or at 1.8 V through an internal electron transfer between TiO₂Li_x and Cu(II) according to the successive reactions: $$\begin{gathered} TiO_2 + xe + xLi^ + \leftrightharpoons TiO_2 Li_x \hfill \\ Cu(II) \xrightarrow{{TiO_{2 } Li_x }} Cu(O), TiO_2 \hfill \\ \end{gathered} $$ This study shows that electrochemistry may be a novel way of determining and controlling the redox states of metal-supported catalysis.     

Mass transfer characteristics of electrochemical reactors employing gas evolving mesh electrodes

Mass transfer rates were measured at a single screen and a fixed bed of closely packed screens for the simultaneous cathodic reduction of K₃Fe(CN)₆ and anodic oxidation of K₄Fe(CN)₆ in alkaline solution with H₂ and O₂ evolution, respectively. Variables studied were gas discharge rate, number of screens per bed and position of the electrode (vertical and horizontal). For single screen electrodes, the mass transfer coefficient was related to the gas discharge rate by the equations: $$\begin{gathered} K = aV^{0.190} , for H_2 evolving electrodes, \hfill \\ K = aV^{0.469} , for O_2 evolving electrodes \hfill \\ \end{gathered} $$ . Electrode position was found to have no effect on the rate of mass transfer for single and multiscreen electrodes in the case of H₂ and O₂ evolution. Mass transfer coefficients were found to increase with an increasing number of screens per bed in the case of H₂ evolution, while in the case of O₂ evolution the mass transfer coefficient decreased with an increasing number of screens per bed. A mathematical model was formulated to account for the behaviour of the H₂ evolving electrode which, unlike the O₂ evolving electrode, did not obey the penetration model. Power consumption calculations have shown that the beneficial effect of mass transfer enhancement is outweighed by the increase in the voltage drop due to gas evolution in the bed electrode.     

Solid state ionics—the electrochemical analog memory cell with solid electrolyte

A new type analog memory cell with variable output voltage has been proposed and its performance examined. The cell construction is $$\begin{gathered} {\text{Ag|RbAg}}_{\text{4}} {\text{I}}_{\text{5}} {\text{|(Ag}}_{\text{2}} {\text{Se)}}_{{\text{0}} \cdot {\text{925}}} {\text{(Ag}}_{\text{3}} {\text{PO}}_{\text{4}} {\text{)}}_{{\text{0}} \cdot {\text{075}}} {\text{|RbAg}}_{\text{4}} {\text{I}}_{\text{5}} {\text{|Ag}} \hfill \\ {\text{ }} \uparrow \hfill \\ {\text{ Pt}} \hfill \\ \end{gathered} $$ in which (Ag₂Se)_0.925(Ag₃PO₄)_0.075 is a mixed conductor exhibiting high ionic and electronic conductivity at room temperature. The potential difference between the silver electrode and the platinum electrode depends on the silver activity in the mixed conductor, and it is changed by passing the current between one silver electrode and the platinum electrode. The output voltage of the cell is changed in the range of 150 to 0 mV. At open circuit, the memorized cell voltage decreased by only 1% over several hours.     

Structure and reactivity of MoO3-MgO catalysts

Surface of OH groups on reduced MoO₂-MgO catalysts such as $$ - - Mg - - O - - \begin{array}{*{20}c} {||} \\ {Mo} \\ | \\ \end{array} - - OH$$ may act as an active site for hydrogenation of propene. The surface hexa-coordinated Mo⁵⁺ ion (MO _6c ⁵⁺ ) was reduced to a lower number of cation such as Mo⁴⁺ or Mo³⁺ which act as an active site for metathesis of propene.     

Branched chain fatty acids and sulfonated derivatives

Several 2-alkyl fatty acids containing 18–21 carbon atoms, were synthesized by tertiary butyl peroxide catalyzed addition of linear aliphatic carboxylic acids to normal terminal olefins. The products obtained in 35–70% yields were purified by fractional distillation. The acids were sulfonated with sulfur trioxide dioxane adduct and isolated as the disodium salts in 60–80% yields.

$$ \begin{gathered} R - CH_2 CO_2 H + R'CH = CH_2 \xrightarrow[{125 - 160C}]{{Perioxide}}R'CH_2 CH_2 - CH(R)CO_2 H \hfill \\ R' - CH_2 CH_2 CH(R)CO_2 H + SO_3 \xrightarrow{{CCl_4 }}R'CH_2 CH_2 C(SO_3 H)(R)CO_2 H \hfill \\ \end{gathered} $$     

Positive polyacetylene electrodes in aqueous electrolytes

Polyacetylene films, contacted with platinum mesh, have been polarized anodically in aqueous H₂SO₄, HClO₄, HBF₄ and H₂F₂ of medium concentrations (30–70 wt%). Two oxidation peaks are observed, the equivalents of which are 1 $${\text{(1) 0}}{\text{.045 F mol}}^{ - {\text{1}}} {\text{ CH (2) 0}}{\text{.23 F mol}}^{ - {\text{1}}} {\text{ CH}}$$ The potential of the Process 1 decreases linearly with increasing acid concentration by 20–40 mV mol^?1 dm^?3, while the potential of Peak 2 exhibits normal Nernst behaviour (about + 60 mV decade^?1. Process 1 is partially reversible, while Process 2 is totally irreversible. From these findings for Process 1 we conclude the reversible insertion of anions into the polyacetylene host lattice, which is primarily oxidized to the polyradical cation, with the co-insertion of acid molecules HA to yield the insertion compound [(CH)⁺·yA^?·vyHA] _x y?4.5% andv=1.5 for H₂SO₄ and HClO₄. In the course of Process 2, the polymer is irreversibly oxidized according to $$( - ^ \cdot {\text{CH}} \cdot \cdot \cdot \cdot \cdot \cdot \cdot \cdot ^ \oplus {\text{ CH}} - )_{x/2} + 2{\text{H}}_{\text{2}} {\text{O}} \to ( - \mathop {\text{C}}\limits_{\mathop \parallel \limits_{\text{O}} } \cdot \cdot \cdot \cdot \cdot \cdot \cdot \cdot \mathop {\text{C}}\limits_{\mathop \parallel \limits_{\text{O}} } - )_{x/2} + 6{\text{H}}^{\text{ + }} + 5e^ - $$ As this process occurs to some extent even in the potential region of Process 1, a continuous degradation of the host lattice occurs upon cycling.     

The corrosion of copper in ethylene glycol-water mixtures containing chloride ions

The anodic oxidation of copper at 25°C in 50% (w/w) ethylene glycol-water and in aqueous solutions has been studied by linear sweep voltammetry. The effect of chloride concentration at pH 0 and 3 has been explored. The results in both solvents follow a similar pattern. At pH 0 and in the absence of chloride, only one anodic peak is observed corresponding to the dissolution of copper metal as copper(II) ions. At intermediate chloride concentrations (0.01–0.03 M), two additional peaks are detected which have been attributed to the following reactions: $$\begin{gathered} Cu + Cl^ - \to CuCl + e^ - \hfill \\ CuCl \to Cu^{2 + } + Cl^ - + e^ - \hfill \\ \end{gathered} $$ When the chloride concentration is increased further, the three peaks gradually collapse back into one, corresponding to the dissolution of copper as a copper(I) chloro-complex. An additional peak appears at pH 3 which has been ascribed to the formation of copper(I) oxide. The results have been interpreted usingE-pCl diagrams determined for the copper-chloride system in both 50% ethylene glycol-water and aqueous solutions. Further information has been obtained from rotating disc measurements and from microscopy. The relevance of these results to corrosion in automotive cooling systems is discussed.