Spectrophotometric study of stability constants of cimetidine–Ni(II) complex at different temperatures

Cimetidine, a histamine H₂-receptor, has a structure which enables it to act as a chelating agent. The formation of nickel(II) complex with cimetidine has been studied spectrophotometrically at an absorption maximum of 622 nm at different temperatures. The data show that nickel(II) and cimetidine combine in the molar ratio of 1:2. The stability constants of the complex were calculated to be 1.40–2.4 × 10⁸ by continuous variation method and 1.24–2.4 × 10⁸ by mole ratio method at 25 and 40 °C, respectively. The immediately formed complex shows stability with respect to time and temperature.     

Phase equilibria in the system Rb3PO4–Ba3(PO4)2

The system Rb₃PO₄–Ba₃(PO₄)₂ was investigated by thermoanalytical methods, X-ray powder diffraction, ICP, and FT-IR. On the basis of the obtained results its phase diagram was proposed. For this system with one intermediate compound, BaRbPO₄, we found that this compound melts congruently at 1700 °C, exhibits a polymorphic transition at 1195 °C and is high-temperature unstable. Also, the intermediate compound was subject to gradual decomposes to Ba₃(PO₄)₂ (the solid phase) and vaporization (with conversion of phosphorus and rubidium oxides into vapor phase). We also found that Rb₃PO₄ melts congruently at 1450 °C and shows a polymorphic transition at 1040 °C. Regarding Ba₃(PO₄)₂, we have confirmed that it melts congruently at 1605 °C and exhibits a polymorphic transition at 1360 °C.     

Studies of the chemical properties of tri-n-octylamine–secondary octanol–kerosene–HCl–H2O microemulsions and its extraction characteristics for cadmium(II)

A new microemulsion system is formed by acidification of tri-n-octylamine–secondary octanol–kerosene with HCl. The system is characterized by conductivity measurement, coloring, dilution, infrared spectroscopy and Tyndall effect. The corresponding results show that the microemulsion is oil-continuous (w/o). The phase diagram is also constructed. Conductivities, viscosities, index of refraction, and densities of the microemulsions system are determined. The activation energy (ΔE) is determined at different temperatures, and implies that a bicontinuous structure zone is not found in the investigated system. Additionally, extraction of cadmium(II) ions by this microemulsion system is also investigated. The corresponding optimum extraction conditions are obtained.     

Phase formation along the PO 4 3− /Zr = 1.5–2.0 section of the ZrO(NO3)2-KF-H3PO4-H2O) system

The phase composition of precipitates at 20°C along the PO ₄ ^3? /Zr = 1.5–2.0 section at KF/Zr = 1–5 (mol/mol) of the ZrO(NO₃)₂-H₃PO₄-KF-H₂O system has been investigated. Phases in these precipitates have been identified by X-ray powder diffraction, crystal-optical, chemical, and thermal analyses and by IR spectroscopy. The previously known potassium zirconates K₃ZrF₇ and K₂ZrF₆ have been revealed, and crystalline fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂ and a phosphate nitrate of unknown formula have been obtained for the first time.     

Individual extraction constants of some organic cations in the two-phase water–nitrobenzene system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium C⁺(aq) + Cs⁺(nb) ⇔ C⁺(nb) + Cs⁺(aq) taking part in the two-phase water–nitrobenzene system (C⁺ = organic cation; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the individual extraction constants of 15 organic cations in the mentioned two-phase system were calculated.     

Phase equilibria in the ErPO4–K3PO4 system

The phase equilibria occurring in the ErPO₄–K₃PO₄ system were investigated by the thermal analysis, FTIR, and X-ray powder diffraction methods. On the basis of obtained results, the related phase diagram is proposed. This system includes one intermediate compound, K₃Er(PO₄)₂; the double phosphate melts incongruently at 1355 °C and occurs in two polymorphic forms; transformation β/α-K₃Er(PO₄)₂ proceeds at 420 °C. The eutectic occurs at the composition of 58.5 wt% K₃PO₄, 41.5 wt% ErPO₄ at 1317 °C.     

Phase equilibria in the YPO4–Rb3PO4 system

The phase equilibria occurring in the YPO₄–Rb₃PO₄ system were investigated by thermoanalytical methods, X-ray powder diffraction, and ICP-OES. On the basis of the obtained results, its phase diagram is proposed. It was found that the system includes two intermediate compounds Rb₃Y(PO₄)₂ and Rb₃Y₂(PO₄)₃. The Rb₃Y(PO₄)₂ compound melts congruently at 1300 °C. The Rb₃Y₂(PO₄)₃ orthophosphate was previously unknown. This intermediate compound is high-temperature unstable and decomposes within the temperature range 1300–1330 °C to YPO₄ and Rb₃Y(PO₄)₂. The decomposition process is irreversible. It was found that the Rb₃Y₂(PO₄)₃ orthophosphate is isostructural with Rb₃Yb₂(PO₄)₃ and crystallizes in the cubic system (a = 1.70226 nm).     

Thermodynamic properties of the system NH4NO3–KNO3–H2O at 298.15 K

The water activity and osmotic coefficients of the system {y NH₄NO₃+(1-y) KNO₃}(aq) has been measured at total molalities from 0.2 mol kg⁻¹ to about saturation of one of the solutes for different ionic-strength fractions y of NH₄NO₃ with y=0.2, 0.5 and 0.8 at the temperature 298.15 K using the hygrometric method. The obtained data allow the deduction of the thermodynamic parameters. From these measurements, new Pitzer ionic mixing parameters are determined and used to predict the solute activity coefficients in the mixture. The results obtained are used to calculate the excess Gibbs energy at total molalities for different ionic-strength fractions of NH₄NO₃.     

Solution and structural studies of the Cd(II) – Aconitate system

The complexing ability of the binary system trans-aconitic acid (H₃L) with regard to Cd(II) and the crystal structures of the binary system Cd(II)–(H₃L), [Cd₃L₂(H₂O)₆] n(1) and ternary systems of Cd(II)–(H₃L)–Lewis base [Lewis base = 1,10-phenanthroline (2) and 2,2′-bipyridine (3)] have been determined. Compound 1 is a rare binodal four-connected three-dimensional (3D) metal-organic framework possessing a moganite (mog) topology. Compounds 2 and 3 represent infinite one-dimensional (1D) chains forming three-dimensional metal-supramolecular structures through H-bond and π–π stacking interactions. All compounds have been characterized by spectroscopic and thermogravimetric techniques.     

Individual extraction constants of some univalent cations in the two-phase water–phenyltrifluoromethyl sulfone system

The preparation and characterization of three different phases of zirconium phosphate (ZrP) have been carried out using XRD, SEM, EDX, and FTIR spectroscopy. The phases exchange and sorption properties with three different radioisotope ²³⁴Th, ²³⁸U, and ¹³⁴Cs were investigated.     

Individual extraction constants of some divalent metal cations in the two-phase water–nitrobenzene system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq) + Sr²⁺(nb) ? M²⁺(nb) + Sr²⁺(aq) taking part in the two-phase water–nitrobenzene system (M²⁺ = Mg²⁺, Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, ${\text{UO}}_{2}^{2 +} $ , Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the individual extraction constants of the M²⁺ cations in the mentioned two-phase system were calculated; they were found to increase in the following cation order: ${\text{UO}}_{2}^{2 + } $  < Zn²⁺, Ni²⁺ < Cu²⁺, Cd²⁺ < Co²⁺ < Mg²⁺ < Ca²⁺ < Mn²⁺, Fe²⁺ < Sr²⁺ < Pb²⁺ < Ba²⁺.     

Thermodynamic properties of the system MgSO4–MnSO4–H2O at 298.15 K

The mixed aqueous electrolyte system magnesium and manganese sulfate has been studied with the hygrometric method at the temperature 298.15 K. The relative humidity of this system is measured at total molalities from 0.2 mol kg⁻¹ to about saturation of one of the solutes for different ionic-strength fractions y of MgSO₄ with y=0.2, 0.5 and 0.8. The obtained data allow the deduction of new thermodynamic parameters. The experimental results are compared with the predictions of ZSR rule. From these measurements, the new Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The obtained results are used to calculate the excess Gibbs energy at total molalities for different ionic-strength fractions y of MgSO₄.     

Investigation of phase equilibria in the Er2O3–Na2O–P2O5 system: the partial system ErPO4–NaPO3–Er(PO3)3

The partial system ErPO₄–NaPO₃–Er(PO₃)₃ of the Er₂O₃–Na₂O–P₂O₅ oxide system has been investigated by thermoanalytical methods and X-ray powder diffraction. On the basis of the obtained results the phase diagram of the partial system is proposed. The system is bounded by three subsystems: (i) ErPO₄–Er(PO₃)₃, (ii) Er(PO₃)₃–NaPO₃ and (iii) ErPO₄–NaPO₃. Their phase diagrams are proposed. In the Er(PO₃)₃–NaPO₃ subsystem an intermediate compound NaEr(PO₃)₄ occurs; it melts incongruently at 655 °C. It was found that ErPO₄ and NaEr(PO₃)₄ form a section which is a real system only in the subsolidus region (below 646 °C). Two ternary invariant points (one ternary peritectic and one ternary eutectic) occur in the investigated partial system ErPO₄–NaPO₃–Er(PO₃)₃.     

An infrared and raman spectroscopic study of pyrazinecadmium (II) tetracyanometalate (II) Benzene (1/1) clathrates: Cd(C4H4N2)Cd(CN)4⁗C6H6 and Cd(C4H4N2)Hg(CN)4⁗C6H6

Two new benzene clathrates of the form Cd(Pyrazine)M(CN)₄C₆H₆, where M = Cd or Hg, have been prepared and their infrared and Raman spectra are reported.     

Liquid–liquid equilibria in the system H3PO4–KCl–H2O–tri-n-butyl phosphate: experiments and modelling

The liquid–liquid equilibria of the system H₃PO₄–KCl–H₂O–TBP was studied experimentally in the concentration range 0–6 mol/kg. The obtained data were modelled using the Pitzer equation for the aqueous phase and the Sergievskii–Dannus relationship for the organic phase. A fairly good agreement was observed between the model and the experimental data.     

Potassium-conducting solid electrolytes in the K3 − 2x Cd x PO4 system

New potassium-conducting solid electrolytes of the K_{3 ? 2x} Cd _x PO₄ system are synthesized and studied. A wide range of solid solutions reaching x ≈ 0.35 with the structure of high-temperature modification of potassium orthophosphate forms in the system. An addition of cadmium ions leads to an abrupt increase in the K₃PO₄ conductivity due to the formation of potassium vacancies. The highest conductivity is approximately 10^?2 S cm^?1 at 300°C and above 10^?1 S cm^?1 at 700°C.     

Solubility equilibria in the system Cd(II)-2-mercaptopropionic acid at 25°C

The solubility equilibria between Cd(II) and 2-mercaptoproprionic acid in 3.0 M NaClO₄ at 25°C have been studied by e.m.f. The e.m.f. measurement with both glass and Cd(Hg) electrodes in the range 2.5 < pH < 4.8 were made in solutions where a solid phase coexists with soluble complexes Cd_qA_p. Free ligand and metal ion concentrations were calculated in order to determine the solubility product of CdA (eqn 5). From the values of the formation constants for the soluble complexes and the solubility product, the solubility constants k_spq have been computed. A general equation for the redissolution of the precipitate is proposed and a set of equilibrium constants is given.