Oxamidato complexes. Part 4. Electrochemical study of the copper(III)/copper(II) couple in monomeric N,N′-bis(substituent)oxamidatocopper(II) complexes

Summary The electrochemical behaviour of a series of monomeric N,N-bis(substituent)oxamidato copper(II) complexes of formula Na₂[Cu(3,5,3,5-X₄obbz)]·4H₂O [X = Cl (1), Br (2), I (3) and obbz = oxamidobis(benzoato)], Na₂-[Cu(obbz)]·4H₂O (4), Na₂[Cu(5,5-Me₂obbz)]·4H₂O (5), Na₂[Cu(4,5,4,5-(MeO)₄obbz)]·4H₂O(6),Na₂[Cu(obp)]· 3.5H₂O (7) (obp = oxamidobis(propionato)) and Na₂[Cu(pba)]·6H₂O (8), [pba = propylenebis(oxamate)] has been investigated by cyclic voltammetry, rotating disk electrode and coulometry in water and dimethylsulphoxide (dmso) solutions. NaNO₃ (0.1 M) and n-Bu₄NPF₆ (0.1 M) were used as supporting electrolytes in H₂O and dmso respectively, all solutions being thermostatted at 25 °C. In aqueous solution, the complexes show an oxidation peak ranging from 1.19 to 0.86 V (values referred to the s.c.e.), the corresponding reduction being unobserved, even at high scan rates. In dmso, all the complexes exhibit only one oxidation peak ranging from 0.86 to 0.51 V, the corresponding reduction being observed for all of them except for (3). The oxidation potentials are strongly dependent upon the nature of the N,N-substituent of the oxamide. The copper(III)-assisted hydrolysis of the oxamidate ligand is analysed in terms of the lack of planarity of the oxamidate ligand induced by the steric effect of the halogen substituent in the 3-position on the phenyl rings. The influence of the nature of the solvent was also studied.     

Koordinationsverbindungen von organischen Oxosubstanzen, 26. Mitt.: Präparation und Eigenschaften der Aluminium-Weinsäure-verbindungen

Zusammenfassung Systematisch wurden, teils durch Eindampfen von Lösungen, teils durch fraktionierte Ausfällung mittels Alkanolen, Stoffe mit verschiedenen molaren Verhältnissen an Aluminium-, Tartratund kompensierenden Natrium- bzw. Sulfationen hergestellt. Das Verhalten bei der Herstellung, die chemischen Eigenschaften, die Röntgendiagramme, die Gewichts- und Differentialthermoanalyse¹⁷ sowie die Infrarot-Spektroskopie²³ zeigten, daß folgende Stoffe als chemische Individuen anzusehen sind (T ^4- ist das vierbasische Anion der Weinsäure C₄H₂O ^4–):Al₂H₂ T(SO₄)₂·6 H₂O, Al₂HT(SO₄)_1,5·6 H₂O, Al₂ TSO₄·6 H₂O, Al₄ T ₃·12 H₂O, NaAlT·3 H₂O, AlH₃ TSO₄·3 H₂O, AlH₂ T(SO₄)_0,5·3 H₂O, AlHT·3 H₂O, Na₂AlTOH·2 H₂O, Na₃AlT(OH)₂·2 H₂O, NaAlH₄ T ₂·3 H₂O, Na₂AlH₃ T ₂·4 H₂O, Na₃AlH₂ T ₂·4 H₂O, Na₄AlHT ₂·5 H₂O, Na₅AlT ₂·4 H₂O.

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A systematic preparation of compounds, containing varying molar ratios of aluminum, sodium, tartrate and sulfate was undertaken. The compounds were precipitated either by concentrating the corresponding solutions, or by fractional precipitation with alcohols. The chemical identity of the 15 compounds was confirmed by their chemical properties, X-ray diffraction, gravimetric analysis, and differential thermoanalysis as well as I.R. spectroscopy.

     

Interaction of Aluminium (III) with the f-Family Ions Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) in the Course of Simultaneous Hydrolysis

The interaction of Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) with Al(III) in solutions at pH 0–4 was studied by the spectrophotometric method. It was shown that, in the range of pH 3–4, the hydrolyzed forms of neptunyl and plutonyl react with the hydrolyzed forms of aluminium. In the case of Pu(VI), the mixed hydroxoaqua complexes (H₂O)₃PuO₂(-OH)₂Al(OH)(H₂O)₃ ²⁺ or (H₂O)₄PuO₂OAl(OH)(H₂O)₄ ²⁺ are formed at the first stage of hydrolysis. Np(VI) also forms similar hydroxoaqua complexes with Al(III). The formation of the mixed hydroxoaqua complexes was also observed when Np(IV) or Pu(IV) was simultaneously hydrolyzed with Al(III) at pH 1.5–2.5. The Np(IV) complex with Al(III) has, most likely, the formula (H₂O) _n (OH)Np(-OH)₂Al(OH)(H₂O)₃ ³⁺. At pH from 2 to 4.1 (when aluminium hydroxide precipitates), the Np(V) or Nd(III) ions exist in solutions with or without Al(III) in similar forms. When pH is increased to 5–5.5, these ions are almost not captured by the aluminium hydroxide precipitate.     

Hydrolyseprodukte von Hexabromoosmat(IV), OsBr62−

Hydrolysis Products of Hexabromoosmate (IV), OsBr₆^2? As a result of the acidic hydrolysis of hexabromoosmate(IV), OsBr₆^2?, products were obtained which were separated by ion column chromatography using diethylaminoethylcellulose. On the basis of the analytically determined Os: Br ratios, the ionic charges that could be deduced from the elution behaviour, and the absorption spectra the products have been characterized as OsBr₅(H₂O)^?, Br₄(H₂O)Os? ;OH? ;Os(H₂O)Br₄^?, Br₃(H₂O)₂Os? ;OH? ;Os(OH)(H₂O)Br₃, Br₂(H₂O)₂(OH)Os? ;OH? ;Os(OH)(H₂O)₂Br₂⁺ and OsBr(OH)_m(H₂O) (0 ? m ? 2). In the dimers intramolecular formation of hydrogen bonds is assumed.     

Speciation of water-soluble titanium citrate: Synthesis,structural, spectroscopic properties and biological relevance

Titanium(IV) citrate complexes with different anions Na₃[Ti(H₂cit)₂(Hcit)] · 9H₂O (1), K₄[Ti(H₂cit)(Hcit)₂] · 4H₂O (2), K₅[Ti(Hcit)₃] · 4H₂O (3) and Na₇[TiH(cit)₃] · 18H₂O (4) (H₄cit = citric acid) were isolated in pure forms from the solutions of titanate and citrate at various pH values. X-ray structural analyses revealed the presence of a monomeric tricitrato titanium unit in the four complexes. Each Ti(IV) ion is coordinated octahedrally by the three citrate ligands in different protonated forms. The citrate ligand chelates bidentately to the titanium ion through its negatively charged α-alkoxy and α-carboxy groups. This is consistent with the large downfield ¹³C NMR shifts for the carbon atoms bearing the α-alkoxy and α-carboxy groups. The very strong hydrogen-bonds existing in the protonated and deprotonated β-carboxy groups may be the key factor for the stabilization of the titanium citrate complexes. When the pH value is lower than 7.0, ¹³C NMR spectra of 1:3 Ti:citrate solutions are similar to those of the titanium citrate complexes isolated at the corresponding pH values. The dissociation of free citrate increases with the rise of pH value. However, ¹³C NMR spectra of 1:3 Ti:citrate solutions indicate that there may exist different citrate titanium species when the pH value is higher than 7.0.     

Thermodynamic representation of the NaCl + Na2SO4 + H2O system with electrolyte NRTL model

A comprehensive thermodynamic model based on the electrolyte NRTL (eNRTL) activity coefficient equation is developed for the NaCl + H₂O binary, the Na₂SO₄ + H₂O binary and the NaCl + Na₂SO₄ + H₂O ternary. The NRTL binary parameters for pairs H₂O-(Na⁺, Cl⁻) and H₂O-(Na⁺, SO₄²⁻), and the aqueous phase infinite dilution heat capacity parameters for ions Cl⁻ and SO₄²⁻ are regressed from fitting experimental data on mean ionic activity coefficient, heat capacity, liquid enthalpy and dissolution enthalpy for the NaCl + H₂O binary and the Na₂SO₄ + H₂O binary with electrolyte concentrations up to saturation and temperature up to 473.15 K. The Gibbs energy of formation, enthalpy of formation and heat capacity parameters for solids NaCl_(s), NaCl·2H₂O_(s), Na₂SO_4(s) and Na₂SO₄·10H₂O_(s) are obtained by fitting experimental data on solubilities of NaCl and Na₂SO₄ in water. The NRTL binary parameters for the (Na⁺, Cl⁻)-(Na⁺, SO₄²⁻) pair are regressed from fitting experimental data on dissolution enthalpies and solubilities for the NaCl + Na₂SO₄ + H₂O ternary.     

Entwässerung von Kristallhydraten als Verfahren zur Reinigung von Salzen, 3. Mitt.: Entwässerung von Na2SO4·10H2O in gesättigter Lösung bei der Temperatur des Übergangs

Zusammenfassung Das Verhalten einer nicht-isomorphen Beimengung bei der Entwässerung von Na₂SO₄·10H₂O bis zum wasserfreien Salz in gesätt. Lösung bei der Temp. des Übergangs wurde untersucht. Es wurde festgestellt, daß der Entwässerungsprozeß von einem Prozeß der Beimengungsverminderung begleitet wird. Dabei wird bei der Re-Hydratisierung des Na₂SO₄ bis zu Na₂SO₄·10 H₂O die Beimengung wieder eingeschlossen. Bei einem geringeren Gehalt an Beimengung in Na₂SO₄·10 H₂O ist der Reinigungseffekt beim Entwässerungsprozeß kleiner und umgekehrt. In der Reihe Cl, Br, J wird — bei sonst gleichen Bedingungen — J am schwierigsten beseitigt, Cl am leichtesten. Außerdem ist die Abhängigkeit zwischen dem Reinigungseffekt (ausgedrückt durch den Reinigungskoeffizienten,W) und dem Ionenradius linear. Die Wasserstoffionenkonzentration in der gesättigten Na₂SO₄·10 H₂O-Lösung übt keinen wesentlichen Einfluß auf die Beseitigung der Beimengung aus.

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Purification of salts by dehydration of crystal hydrates, III: Dehydration of Na₂SO₄·10 H₂O in saturated solution at the transition temperature

The behaviour of a non-isomorphous admixture in the dehydration of Na₂SO₄·10 H₂O to the anhydrous salt in a saturated solution at the transition temperature has been investigated. It was found that a decrease of admixture accompanies the dehydration process. The admixture is reincluded during rehydration of Na₂SO₄ to Na₂SO₄·10 H₂O. With a lower admixture content, the purification achieved during dehydration of Na₂SO₄·10 H₂O is less marked, and vice versa. In the series Cl, Br, I, other conditions being equal, I is hardest to remove, Cl easiest. It was further found that a linear relationship exists between the purifying effect (expressed by the purification coefficient,W) and the ion radius. The hydrogen ion concentration has no significant influence on the removal of the admixture.

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Mit 6 Abbildungen     

Arrangement and Diffusive Mobility of Extraframework Species in the Hydrated Ammonium Forms of Zeolites Clinoptilolite and Chabazite

The location and diffusive mobility of ammonium ions and water molecules in the channels of the NH₄substituted forms of the natural zeolites clinoptilolite (NH₄)_6.5[Al_6.5Si_29.5O₇₂] · 12.6H₂O and chabazite (NH₄)_9.6Ca_0.6Na_0.3[Al_11.1Si_24.9O₇₂] · 25.8H₂O were studied by Xray diffraction analysis and ¹H NMR spectroscopy. The arrangement of the extraframework subsystem was shown to be largely determined by hydrogen bonds N—H...O(H₂O) of length 2.7–2.9 . The diffusive mobility of the ions was found to correspond to abnormally low energy barriers, similar to those for H₂O diffusion. The activation parameters for the diffusion jumps of the ions and molecules are E(NH₄) = E(H₂O) = 31(2) kJ/mole, ₀(NH₄) = 2 · 10¹¹ sec^-1, ₀(H₂O) = 4 · 10¹² sec^-1 in NH₄chabazite and E(NH₄) = E(H₂O) = 25(1) kJ/mole, ₀(NH₄) = 2 · 10¹⁰ sec^-1, ₀(H₂O) = 3 · 10¹¹ sec^-1 in NH₄clinoptilolite. It is suggested that the development of ion and molecular diffusion is caused by the same defects, whose formation with temperature rise is controlled by Hbond rearrangement.     

The crystal chemistry of four thorium sulfates

Four thorium sulfate compounds have been synthesized and characterized. [Th(SO₄)₂(H₂O)₇]·2H₂O (ThS1) crystallizes in space group P2₁/m, a=7.2488(4), b=12.1798(7), c=8.0625(5) Å, β=98.245(1)^o; Na₁₀[Th₂(SO₄)₉(H₂O)₂]·3H₂O (ThS2), Pna2₁, a=17.842(2), b=6.9317(8), c=27.550(3) Å; Na₂[Th₂(SO₄)₅(H₂O)₃]·H₂O (ThS3), C2/c, a=16.639(2), b=9.081(1), c=25.078(3) Å, β= 95.322(2)^o; [Th₄(SO₄)₇(OH)₂(H₂O)₆]·2H₂O (ThS4), Pnma, a=18.2127(9), b=11.1669(5), c=14.4705(7) Å. In all cases the Th cations are coordinated by nine O atoms corresponding to SO₄ tetrahedra, OH groups, and H₂O groups. The structural unit of ThS1 is an isolated cluster consisting of a single Th polyhedron with two monodentate SO₄ tetrahedra and seven H₂O groups. A double-wide Th sulfate chain is the basis of ThS2. The structures of ThS3 and ThS4 are frameworks of Th polyhedra and sulfate tetrahedra, and each contains channels that extend through the framework. One of the Th cations in ThS3 is coordinated by a bidentate SO₄ tetrahedron, and ThS4 is unusual in the presence of a pair of Th cations that share a polyhedral face.     

The Solubility of Sodium Sulfate and the Reduction of Aqueous Sulfate by Magnetite under Near-Critical Conditions

The solubility of Na₂SO₄ (s) (thenardite) and the interactions between magnetiteand aqueous Na₂SO₄ near the critical point of water have been determined in azirconium-alloy flow reactor at temperatures 350°C t 375°C and isobaricpressures 190 p 305 bar. The experimental solubility data are describedwell as a function of temperature and solvent density ₁ byln x(Na₂SO₄, aq.) = –10.47 – 27550/T +(4805/T) ln ₁.The interaction between magnetite and Na₂SO₄ (aq.) was examined from 250 to370°C at molalities near the saturation composition of Na₂SO₄ (s). While no solidreaction products were observed, HS^– (aq.) was observed to form above 350°Cby sulfate reduction, as a product of the reaction8 Fe₃O₄(s) + Na₂SO₄ (aq.) + H₂O(l)= 12 Fe₂O₃ (s) + NaHS (aq.) + NaOH (aq.).The reduction reaction appears to be controlled by surface reaction kinetics, ata level well below the equilibrium molality of HS^– (aq.). Metallic iron reactedwith Na₂SO₄ (aq.) in a similar fashion at temperatures above 350°C, to yieldhigher molalities of HS^– (aq.).     

Ruthenium(IV) and Osmium(II) Tetraphenylporphine Complexes: Synthesis and Oxidation Reactions

The Ru(IV) and Os(II) complexes (PhO)₂RuTPP and OsTPP were synthesized from tetraphenylporphine (H₂TPP) and K₂RuO₄ or K₂OsO₄ (taken in the molar ratio of 1 : 30) in boiling phenol. The kinetics of oxidation reactions of these complexes in solutions of HOAc (acetic), H₂SO₄, and HOAc–H₂SO₄ acids was studied. It was found that in the aerated HOAc–H₂SO₄ mixture heated above 340 K, these complexes are oxidized with participation of different reaction sites: the Ru(IV) complex is oxidized at macrocycle to give the -radical-cation (PhO)₂RuPP⁺, while in the Os(II) complex, the metal atom is oxidized to form the Os(III) complex. In the first case, the reaction follows the activation mechanism, whereas in the second case, the activation energy of the reaction is zero.     

Synthesis, structure, and properties of chromium(III) sulfates

Reactions between CrO₃ and 50- are studied at temperatures up to the boiling point of the acid. Depending on the H₂SO₄ concentration and synthesis temperature, Cr₂(SO₄)₃, CrH(SO₄)₂, (H₃O)[Cr(SO₄)₂], Cr₂(SO₄)₃·H₂SO₄·4H₂O (gross formula), and (H₅O₂)[Cr(H₂O)₂(SO₄)₂], are obtained as identified reaction products in addition to the incompletely characterized chromic-sulfuric acid. The Cr^III-based sulfates are characterized by X-ray powder diffraction, thermogravimetric, and magnetic susceptibility measurements. The nuclear and magnetic structures of Cr₂(SO₄)₃ at are determined, the structure type of (H₃O)[Cr(SO₄)₂] is established, and the crystal structure of (H₅O₂)[Cr(H₂O)₂(SO₄)₂] is firmly stipulated. Magnetic susceptibility data suggest that the samples of CrH(SO₄)₂ are in a micro-crystalline rather than in an amorphous state. All Cr^III-based sulfates synthesized in this study appear to undergo paramagnetic-to-antiferromagnetic transitions at around .     

Lowervalent hexaniobate cluster in aqueous HCl: an equilibrium redox study

Summary It has been established⁽¹⁾ that hydrated niobium(V) oxide is, in fact, hexameric isopolyniobic acid, H₈Nb₆O₁₉·xH₂O, containing a protonated oxoniobate(V) cluster. It has also been shown^(2,3) that the stoichiometric and nonstoichiometric oxides as well as niobates, soluble or insoluble, formed under various conditions, are really derivatives of H₈Nb₆O₁₉. The amphoteric H₈Nb₆O₁₉ is soluble in conc. H₂SO₄ maintaining its hexanuclear structure⁽⁴⁾ and exists in the form of a SO₃ adduct of H₈Nb₆O₁₉. In the latest communication⁽⁵⁾ the hexameric cluster has been shown to exist even in the subnormal niobium oxidation states. The aqueous H₂SO₄ solution of niobium(V) when reduced with zinc forms various dark red-brown crystalline salts of the anion [Nb₆O₇(O·SO₃)₁₂]^16–. This cluster anion has niobium in an average nonintegral oxidation state of +3.67 and the Nb₆O₁₉ unit is coordinated to a maximum of twelve SO₃ groups. The present communication describes the potentiometric investigation of the reduced oxoniobate cluster in aqueous HCl. There are reports that strongly acidic niobium(V) solutions are reduced either electrolytically or by metals^(6–9). These workers proposed that niobium(III) was formed in solution although no detailed investigation on the species was made.     

Effect of the structure of frozen solutions of H2SO4 on radiothermoluminescence

A pronounced effect of structural heterogeneity (cracks) of glass-like solutions of 4.9M H₂SO₄ on their radiothermoluminescence (RTL) was found. In perfect glasses one RTL peak was observed at 115 K. Additional luminescence peaks appeared at 165, 195, and 240 K in glasses having cracks. The effect observed was explained by elevated thermal stability of the SO₄ ^– radical stabilized on the surface of sulfuric acid crystal hydrates: H₂SO₄ · 4H₂O and H₂SO₄· 6.5H₂O.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1566–1568, June, 1996.     

Syntheses and crystal structures of straight or zigzag one-dimensional coordination polymers based on Cu(II) square pyramidal or Cu(I) tetrahedral coordination environments

Two coordination polymers containing copper ions, [Cu(SO₄)(pyz)(H₂O)]_n (1) and [Cu₂(SO₄)(pyz)₂(H₂O)₂]_n (2) (pyz = pyrazine), have been synthesized and characterized by single-crystal X-ray analyses. Compound 1 was synthesized by the reaction of Cu(SO₄) · 5H₂O with pyz (ratio = 1:2) in H₂O at room temperature. The structure of 1 consists of linear chains of [Cu(pyz)(H₂O)]²⁺, with coordinated sulfate ions bridging the chains. Compound 2 was obtained as dark red blocks from the reaction of Cu(SO₄) · 5H₂O and pyz (ratio = 1:2) in H₂O, after heating to 180 °C in a Teflon autoclave for 48 h. The structure of 2 consists of zigzag chains of [Cu(pyz)(H₂O)]⁺ with sulfate ions. Only the difference in the synthesis temperature, room temperature or 180 °C, determines whether Cu(II) or Cu(I) coordination polymers are formed, with the reduction of Cu(II) to Cu(I) being explained by the Gillard mechanism.     

Nickel surface anodic oxidation and electrocatalysis of oxygen evolution

The processes of nickel surface anodic oxidation taking place within the range of potentials preceding oxygen evolution reaction (OER) in the solutions of 1 M KOH, 0.5 M K₂SO₄, and 0.5 M H₂SO₄ have been analyzed in the present paper. Metallic nickel, thermally oxidized nickel, and black nickel coating were used as Ni electrodes. The methods of cyclic voltammetry and X-ray photoelectron spectroscopy were employed. The study was undertaken with a view to find the evidence of peroxide-type nickel surface compounds formation in the course of OER on the Ni electrode surface. On the basis of experimental results and literature data, it has been suggested that in alkaline solution at E ≈ 1.5 V (RHE) reversible electrochemical formation of Ni(IV) peroxide takes place according to the reaction as follows: This reaction accounts for both the underpotential (with respect to ) formation of O₂ from NiOO₂ peroxide and also small experimental values of dE/dlgi slope (<60 mV) at low anodic current densities, which are characteristic for the two-electron transfer process. It has been inferred that the composition of the γ-NiOOH phase, indicated in the Bode and revised Pourbaix diagrams, should be ∼5/6 NiOOH + ∼1/6 NiOO₂. The schemes demonstrating potential-dependent transitions between Ni surface oxygen compounds are presented, and the electrocatalytic mechanisms of OER in alkaline, acid, and neutral medium have been proposed.     

Preparation and electrochemical properties of SAM of alkanethiols functionalized with 2-aza[3]ferrocenophane on gold electrode

Thiols functionalized with N-aryl[3]azaferrocenophane formulated as HS-(CH₂)_n-N(CH₂Cp)₂Fe (1: n = 6, 2: n = 8, 3: n = 10, 4: n = 12) and disulfide obtained by oxidation of 4 (5) were synthesized via three or four steps reactions starting from 1,1′-ferrocenedimethanol, 4-aminophenol, and α,ω-aklanedithiol. Self-assembled monolayers (SAMs) of these thiols and disulfide on gold electrode were prepared by immersing the electrode in MeCN solutions of the compounds. Cyclic voltammograms of the SAM of 1 (n = 6) exhibited reversible redox of the Fe center at E_1/2 = 0.26 V (vs. Ag⁺/Ag) in the presence of Et₄NBF₄ in MeCN and at E_1/2 = 0.40 V (vs. AgCl/Ag) in the presence of NaClO₄ in H₂O. Addition of HClO₄ to the solutions shifted the redox peaks to higher potentials, E_1/2 = 0.51 V (vs. Ag⁺/Ag) in MeCN and E_1/2 = 0.48 V (vs. AgCl/Ag) in H₂O, respectively, which was ascribed to positive charge of tertiary ammonium group formed by protonation of the amino group of the azaferrocenophane. E_1/2 of SAM of 1 in H₂O solution varies depending on the anion contained in the electrolyte, NaClO₄ (0.40 V), NaBF₄ (0.46 V), Na₂SO₄ (0.53 V), and NaCl (0.55 V). Kinetic data of electron transfer between the Fe center and the gold surface of the SAM of 2-4 were obtained with variable scanning rate. Laviron’s analysis provided tunneling constant β, 0.05 Å⁻¹, suggesting that the structural changes in the SAMs on oxidation/reduction undergoes the insignificant change of the kinetic constants of the electron transfer depending on the range of the spacer length. In the acidic aqueous media, the kinetic parameters indicated that the imbalanced electron transfer between oxidized and reduced states of the Fe center was caused by the protonation of bridged amine group of azaferrocenophane.     

Solid–liquid metastable equilibria in the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K

Solubility in the liquid–solid metastable system Li₂SO₄ + MgSO₄ + Na₂SO₄ + H₂O at T = 263.15 K was studied using the isothermal evaporation method. Based on experimental data, dry-salt phase and water-phase diagrams of the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturation point, three metastable solubility isotherm curves, and three crystallization regions corresponding to lithium sulphate monohydrate (Li₂SO₄·H₂O), epsomite (MgSO₄·7H₂O), and mirabilite (Na₂SO₄·10H₂O). Neither a solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β⁽⁰⁾, β⁽¹⁾, β⁽²⁾, and C^Φ for Li₂SO₄, MgSO₄, and Na₂SO₄, the mixed ion-interaction parameters θ_Li,Na, θ_Li,Mg, θ_Na,Mg, ΨLi,Na,SO₄${\Psi }_{\text{Li,Na,S}{\text{O}}_4}$, ΨLi,Mg,SO₄${\Psi }_{\text{Li,Mg,S}{\text{O}}_4}$, and ΨNa,Mg,SO₄${\Psi }_{\text{Na,Mg,S}{\text{O}}_4}$, and the Debye–Hückel parameter A^Φ in the quaternary system at 263.15 K were obtained. The solubility of the quaternary system Li₂SO₄ + MgSO₄ + Na₂SO₄ + H₂O at T = 263.15 K was also calculated. A comparison between the calculated and experimental results shows that the predicted solubility agrees well with experimental data.     

Untersuchung des Systems NaAl(SO4)2?CsAl(SO4)2?H2O bei 25°C und der daraus entstehenden festen Phasen

The solubility diagram of the system NaAl(SO₄)₂–CsAl(SO₄)₂–H₂O was investigated at 25°C. This is a system in which -and -alums participate. The fields of cristallization are outlined. There is one wide field of cesium aluminium alum and one, very narrow, of sodium aluminium alum. The eutonic point of the system lies at the composition of the liquid phase corresponding to 27.90 wt.% NaAl(SO₄)₂ and 0.008 wt.% CsAl(SO₄)₂. It was found that mixed crystals are not formed in the system. The solid phases were investigated by X-ray diffraction andDTA.