Temperature dependence of europium carbonate complexation

The temperature dependencies of europium carbonate stability constants were examined at 15, 25, and 35°C in 0.68 molal Na⁺(ClO ₄ ^? , HCO ₃ ^? ) using a tributyl phosphate solvent extration technique. Our distribution data can be explained by the equilibria $$\begin{gathered} Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuCO_3^ + + 2H^ + \hfill \\ - log\beta _{12} = 9.607 + 496(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + 2H_2 O + 2CO_2 (g)_ \leftarrow ^ \to Eu(CO_3 )_2^ - + 4H^ + \hfill \\ - log\beta _{24} = 21.951 + 670(t + 273.16)^{ - 1} \hfill \\ Eu^{3 + } + H_2 O + CO_2 (g)_ \leftarrow ^ \to EuHCO_3^{2 + } + H^ + \hfill \\ - log\beta _{11} = 1.688 + 1397(t + 273.16)^{ - 1} \hfill \\ \end{gathered}$$      

The thermodynamic characteristics of hydrogen peroxide in H2SO4-H2O solutions

The paper presents experimental data and an analysis of literature data on hydrogen peroxide forms in concentrated solutions of sulfuric acid, H₂O₂(aq), H₃O ₂ ⁺ (aq), and HSO ₅ ^? (aq). The thermodynamic constants of the parallel equilibria $\begin{array}{*{20}c} {H_2 O_2 (aq) + H_3 O^ + (aq) \Leftrightarrow H_3 O_2^ + (aq) + H_2 O (K_1 (298) = 8 \times 10^{ - 4} ),} \\ {H_2 O_2 (aq) + HSO_4^ - (aq) \Leftrightarrow HSO_5^ - (aq) + H_2 O (K_2 (298) = 1.2 \times 10^{ - 2} )} \\ \end{array} $ were determined. The activity coefficients of H₂O₂ and Henry constants for solutions of H₂O₂ in sulfuric acid were calculated.     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

The solvent extraction of Yb(III) and Ho(III) by 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous-methanol phase has been studied as a function ofpH ^× and the concentration ofPAN or methanol (MeOH) in the organic phase. When the aqueous phase contains above ～25%v/v of methanol the synergistic effect was increased. The equation for the extraction reaction has been suggested as: $$\begin{gathered} Ln(H_2 0)_{m(p)}^{3 + } + 3 HL_{(o)} + t MeOH_{(o)} \mathop \rightleftharpoons \limits^{K_{ex} } \hfill \\ LnL_3 (MeOH)_{t(o)} + 3 H_{(p)}^ + + m H_2 0 \hfill \\ \end{gathered} $$ where:Ln ³⁺=Yb, Ho; $$\begin{gathered} t = 3 for C_{MeOH in.} \varepsilon \left( { \sim 25 - 50} \right)\% {\upsilon \mathord{\left/ {\vphantom {\upsilon \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon }; \hfill \\ t = 0 for C_{MeOH in.} \varepsilon \left( { \sim 5 - 25} \right)\% {\upsilon \mathord{\left/ {\vphantom {\upsilon \upsilon }} \right. \kern-\nulldelimiterspace} \upsilon } \hfill \\ \end{gathered} $$ . The extraction equilibrium constants (K _ex ) and the two-phase stability constants (β ₃ ^× ) for theLnL ₃(MeOH)₃ complexes have been evaluated.     

The solubility of magnetite and the hydrolysis and oxidation of Fe2+ in water to 300°C

The solubility of carefully characterized magnetite, Fe₃O₄, in dilute aqueous solutions saturated with H₂ has been measured at temperatures from 100 to 300°C in a flow apparatus. Solution compositions included either HCl or NaOH molalities of up to 1 and 40 mmole-kg^?1, respectively, and H₂ molalities of 0.0779, 0.779, and 8.57 mmole-kg^?1. The dependence of the equilibrium solubility on the pH and reduction potential were fitted to a scheme of soluble ferrous and ferric species consisting of Fe²⁺, FeOH⁺, Fe(OH)₂, Fe(OH) ₃ ^? , Fe(OH)₃, and Fe(OH) ₄ ^? . Solubility products from the fit, corresponding to the reactions $$\tfrac{1}{3}Fe_3 O_4 + (2 - b)H^ + + \tfrac{1}{3}H_2 \rightleftharpoons Fe(OH)_b^{2 - b} + (4/3 - b)H_2 O$$ and $$\tfrac{1}{3}Fe_3 O_4 + (3 - b)H^ + \rightleftharpoons Fe(OH)_b^{3 - b} + \tfrac{1}{6}H_2 + (4/3 - b)H_2 O$$ were used to derive thermodynamic constants for each species. The extrapolared value for the Gibbs energy of formation of Fe²⁺ at 25°C is ?88.92±2.0 kJ-mole^?1, consistent with standard reduction potentials in the range E^o(Fe²⁺)=?0.47±0.01 V. The temperature coefficient of the equilibrium Fe molality, (?m(Fe, sat.)/?T)_{m(H2).m(NaOH)}, changes from negative to positive as the NaOH molality is increased to the point where Fe(OH) ₃ ^? and Fe(OH) ₄ ^? predominate.     

Kinetik der Diazotierung des α-Naphthylamins in wäßriger Chlorwasserstofflösung I.

The kinetics of the diazotization of α-naphthylamine¹ in water HCl solution from 0,2N to 2.0N at 0 °C were investigated. It was found that the nitrosation reaction $$\alpha --C_{10} H_7 NH_2 + NOCl\mathop \rightleftharpoons \limits^{k_v } \alpha --C_{10} H_7 NH_2 NO^ + + Cl^ - $$ is a preceeding advance-back-reaction (velocity coefficient of the nitrosation is 1.92·10¹⁰l mol^?1 s^?1). The decomposition of I by splitting off a proton is the rate determining reaction. The free enthalpy of activation for the nitrosation reaction equals 12.94 kJ/mol.     

Polyhydroxysäuren als Komplexbildner

The reaction of mucic acid (H₆ Mu) with Cobalt(II) and Nickel(II) ions has been studied in 1.0M-Na⁺(NO ₃ ^? ) ionic medium at 25° C using a glass electrode. The e.m.f. data in the range 8≦?log [H⁺]≦10 are explained by assuming $$\begin{gathered} Me^{2 + } + H_4 Mu^{2 - } \rightleftharpoons MeH_3 Mu^ - + H^ + \beta ''_1 \hfill \\ Me^{2 + } + H_4 Mu^{2 - } \rightleftharpoons MeH_2 Mu^{2 - } + 2 H^ + \beta ''_2 \hfill \\ \end{gathered}$$ with equilibrium constants log β′₁ = — 9.36; — 9.34; log β′₂ = — 18.11; — 18.08 for Co(II) and Ni(II) resp.     

Protonierungskonstanten der 8-Hydroxychinolinat-Ionen bei 25°C und in 1m-NaClO4

The protonation of the 8-hydroxyquinolinate ion (Ox ^?) has been studied at 25°C in 1m-NaClO₄ by the potentiometric method and the distribution between CHCl₃ and H₂O. The experimental data are explained by the following equilibria: $$\begin{array}{*{20}c} {H^ + + Ox^ - \rightleftharpoons HOx} \\ {H^ + + Ox \rightleftharpoons H_2 Ox^ + } \\ {HOx_w \rightleftharpoons HOx_{org} } \\ \end{array} \begin{array}{*{20}c} {\log k_1 = 9.42 \pm 0.08} \\ {\log k_2 = 5.46 \pm 0.10} \\ {\log \lambda = 2.40 \pm 0.10} \\ \end{array} $$      

Die kathodische Reduktion von Ozon in alkalischen Elektrolyten

The cathodic reduction of ozone according to the overall reaction O₃+H₂O+2e→O₂+2OH^? was studied on bright platinum electrodes in KOH electrolytes. The rest potentials deviate from the theoretical values by ?300 to ?350 mV. They are determined by a mixed potential mechanism involving anodic evolution of O₂ and cathodic reduction of O₃ as half reactions. Steady-state polarization measurements were carried out. Extrapolation of Tafel-lines to zero over-voltage and the determination of the charge transfer resistance give current densities at the rest potential, which are analogous to exchange current densities. A single electron transfer reaction is found to be the rate controlling step, which is occurring twice for the reduction of one molecule of ozone. A cathodic reaction order of approximately zero is evaluated with respect to OH^?-ion concentration. The reaction mechanism is proposed according to $$\begin{gathered} O_3 + e \to O_3 - / \cdot 2 \hfill \\ 2O_3 - + H_2 O \to 2 OH - + O_2 + O_3 \hfill \\ \end{gathered} $$ which is consistent with experimental data.     

Zur thermischen Zersetzung der hochkonzentrierten Salpetersäure

The thermal decomposition of highly concentrated nitric acid was observed at atmospheric pressure between 0 and 60 °C for up to 273 d. The decomposition of highly concentrated nitric acid $$2 HNO_3 \rightleftharpoons 2 NO_2 + H_2 O + {1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2} O_2 $$ is a second order reaction in nitric acid. The reversible reaction proceeds to equilibrium. The velocity and equilibrium constants were obtained by kinetic evaluation of the readings for HNO₃ and NO₂. The activation energy for decomposition was — 134 kJ/mol.     

Prediction of the minimum solubility during either deoxidation or desulfurization process in liquid alloys

Deoxidation and desulfurization processes in liquid metallic alloys can be described by four different types of chemical reactions: $$\begin{gathered} xM + yO \to M_x O_y \hfill \\ A + 2M + 4O \to AM_2 O_4 \hfill \\ S + MO \to O + MS \hfill \\ R_2 O_3 + S \to R_2 O_2 S + O \hfill \\ \end{gathered} $$ A state of equilibrium between metallic phase and the reaction products was assumed. A computer procedure, which enables the prediction of the solubility curve and the respective minimum solubility composition, has been developed. The presented approach was tested on Fe-Cr-O, Cu-Mn-O and Fe-O-S dilute solutions. It was found that the value of the interaction parameter ε _O ^Mn in liquid copper reported in the literature is too high. Own experiments suggest a value of ε _O ^Mn =?220 at 1 373 K.     

Reaction between chromium(III) oxide and oxygen in the presence of sodium carbonate

The large scale manufacture of sodium chromate is carried out by heating finely ground chromite ore mixed with sodium carbonate and lime in air. The essential reaction leading to the formation of sodium chromate is $$2Cr_2 O_3 + 4 Na_2 CO_3 + 3 O_2 \xrightarrow{{\Delta {\rm H}_{R^0 } }}4Na_2 CrO_4 + CO_2 $$      

The extraction of Yb(III) and Lu(III) with chloroform from aqueous solutions in the presence of cupferron

The equilibrium of distribution of Yb(III) and Lu(III) between chloroform and the aqueous phase in the presence of cupferron (the ammonium salt of N-nitrosophenylhydroxylamine) were studied as apH function of the aqueous phase and the concentration of N-nitrosophenylhydroxylamine (HL). The stability constants for theLnL _n ^3–n ) complexes (n=1÷3) being formed in the aqueous phase were established, as well as the equilibrium constants of the extraction reaction $$Ln(H_2 O)_m^{3 + } + 3HL_{(O)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(O)} + 3H^ + + mH_2 O(Ln^{3 + } = Yb,Lu),$$ two-phase stability constants for theLnL ₃ complexes,pH _0.5 and the separation factor Lu(III) from Yb(III).     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

Extraction of lutetium(III) and erbium(III) with 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous solutions was examined. The composition of the complex extracted was determined and it was found that the extraction process can be described by the following equation (Ln ³⁺=Lu, Er): $$Ln(H_2 O)_m^{3 + } + 3 HL_{(0)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(0)} + 3 H^ + + mH_2 O$$ The extraction constants (K _ex ) and two-phase stability constants (β ₃ ^x ) forLnL ₃ complexes have been evaluated.     

Kinetik und Mechanismus der Oxydation von 1,2,4,5-Tetramethylbenzol in essigsaurem Medium

The liquid phase oxidation of 1.2.4.5-tetramethylbenzene catalysed by cobaltous acetate and promoted by KBr in acetic acid was kinetically studied. In view of deriving the kinetic equation for the absorption of oxygen, a number of experiments were carried out. The values of the activation energy and of the preexponentA=10¹⁴ were determined as well. The resulting kinetic equation: $$ - \frac{{d\left[ {O_2 } \right]}}{{d\tau }} = 10^{14} \cdot \exp \left( { - \frac{{84,460 \times 10^3 }}{{RT}}} \right) \cdot C_{C_6 H_2 (CH_3 )_4 }^{0,5} \cdot C_{Co(OAc)_2 }^{0,5} \cdot C_{KBr}^{0,5} $$ is in accordance with the theoretically derived expression of this type.     

Synergistic extraction of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate and bis(diphenylphosphino)methane dioxide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of bis(diphenylphosphino)methane dioxide (DPPMDO, L) has been investigated. The equilibrium data have been explained assuming that the species $ {\text{HL}}^{ + } $ , $ {\text{HL}}_{2}^{ + } $ , $ {\text{ML}}_{2}^{3 + } $ , $ {\text{ML}}_{3}^{3 + } $ and $ {\text{ML}}_{4}^{3 + } $ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes $ {\text{EuL}}_{n}^{3 + } $ and $ {\text{AmL}}_{n}^{3 + } $ , where n = 2, 3 and L is DPPMDO, in water–saturated nitrobenzene are comparable, whereas in this medium the stability of the cationic species $ {\text{AmL}}_{4}^{3 + } $ (L = DPPMDO) is somewhat higher than that of $ {\text{EuL}}_{4}^{3 + } $ with the same ligand L.     

Magnesium ionophore III as an effective receptor for trivalent europium and americium

Solvent extraction of microamounts of trivalent europium and americium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate (H⁺B^?) and magnesium ionophore III (L) was studied. The equilibrium data were explained assuming that the species HL⁺, \( \text{HL}_{2}^{ + } , \) \( {\text{ML}}_{2}^{3 + } , \) and \( {\text{ML}}_{3}^{3 + } \) (M³⁺ = Eu³⁺, Am³⁺; L = magnesium ionophore III) are extracted into the nitrobenzene phase. The values of extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed.     

Die kathodische Sauerstoffreduktion an pyrolytisch abgeschiedenem Kohlenstoff in peroxidhältigen alkalischen Elektrolyten

The kinetics of the system O₂/HO₂ ^?, OH^? were studied at pyrolytic carbon in alkaline electrolytes. The rest potentials are close to the reversible values. They decrease by 30 mV when the HO₂ ^?-concentration is increased by a factor 10. CathodicTafel lines displayb-values between 70 and 95 mV. The exchange current densities are evaluated by extrapolation ofTafel lines to zero overvoltage and from the charge transfer resistance. Two different succeeding charge transfer reactions occur in course of the overall process, the first of which is the rate-determining step. A cathodic reaction order of zero is obtained with respect to HO₂ ^?. Theb values of anodicTafel lines are between 60 and 80 mV, the corresponding reaction order concerning the HO₂ ^? concentration is found to be +0.5. The kinetic studies prove the reversibility of the system O₂/HO₂ ^?, OH^? at carbon electrodes. The reaction mechanism is: $$\begin{array}{*{20}c} {O_2 + e^ - \rightleftarrows O_2 } \\ {O_{2^ - } + H_2 O \rightleftarrows HO_2 + OH - } \\ {HO_2 + e^ - \rightleftarrows HO_{2^ - } } \\ \end{array} $$ .     

Solvent extraction of zinc/II/ with sulphoxides: Theoretical analysis of extraction behaviour

This paper describes a theoretical method for analyzing the behaviour of⁶⁵Zn during solvent extraction from ammonium thiocyanate solutions with dialkyl sulphoxides. The mechanism of extraction of Zn/II/ from thiocyanate medium by sulphoxides may be represented by the following general equation: $$xM_{aq}^{m + } + ySCN_{aq}^ - + zS_{org} \rightleftharpoons [M_x /SCN/_y ]^{mx - y} .zS_{org} $$ where M^m+ is the metal ion and S is the extractant. Expressions for the distribution coefficients were derived taking into account complexation of the metal in the aqueous phase by inorganic ligands and also the dissociation of the extracted ion-pairs in the organic phase. Using these expressions, the values of the extraction constants were determined by a least-squares fit with the experimental extraction data. From these extraction constants, the various species extracted into the organic phase were resolved. The influence of the metal concentration, temperature and the diluent on the extraction of Zn/II/ has been investigated.     

Bemerkungen über Thermochromie von Kobalt(II) chloridlösungen in organischen Medien, 1. Mitt.: Lösungen in verschiedenen Alkoholen

The thermochromism of solutions of cobalt(II) chloride in methanol, ethanol, n- and iso-propyl, n-, iso- and sec. butyl alcohol was studied spectrophotometrically. The blue color of these solutions fades with decreasing temperature, solutions in primary alcohols being especially variable, becoming pink at sufficiently low temperature. Solutions in secondary alcohols are, on the other hand, much less variable. The thermochromism can be ascribed, in general, to the shift of the equilibrium $$[CoL_2 Cl_2 ] + (3 - 4) L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} ([CoL_5 Cl]^ + or [CoL_6 ]^{2 + } ) + (1 - 2) Cl^ - $$ (L: solvent molecule). In the case of methanol, however, the two equilibria $$[CoLCl_3 ]^ - + 4 L \begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} [CoL_5 Cl]^ + + 2 Cl^ - $$ and $$[CoL_5 Cl]^ + + L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} [CoL_6 ]^{2 + } ) + Cl^ - $$ seem to be shifted one after another. The significance of the difference between primary and secondary alcohols is briefly discussed in connection with some related effects, i.e. the pressure effect studied byKitamura andOsugi ⁷ and the water effect found byKato et al.¹⁰.     

Komplexe zwischen Eisen(II)- und Tartrat-Ion

The formation of complexes between iron(II) and tartrate ion (L) has been studied at 25° C in 1m-NaClO₄, by using a glass electrode. The e.m.f. data are explained with the following equilibria: $$\begin{gathered} Fe^{2 + } + L \rightleftarrows FeL log \beta _1 = 1,43 \pm 0,05 \hfill \\ Fe^{2 + } + 2L \rightleftarrows FeL_2 log \beta _2 = 2,50 \pm 0,05 \hfill \\\end{gathered} $$ The protonation constants of the tartaric acid have been determinated: $$\begin{gathered} H^ + + L \rightleftarrows HL logk_1 = 3,84 \pm 0,03 \hfill \\ 2H^ + + L \rightleftarrows H_2 L logk_2 = 6,43 \pm 0,02 \hfill \\\end{gathered}$$ .