Thermal analysis of the oxide–chloride systems GdCl3–Gd2O3 and GdCl3–KCl–Gd2O3

Journal of Thermal Analysis and Calorimetry - The thermal analysis of the oxide–chloride systems GdCl3–Gd2O3 and GdCl3–KCl–Gd2O3 with the Gd2O3 content up to...     

Solubility in the LaCl3-YbCl3-HCl-H2O System at 25°C

Solubility has been studied in the LaCl₃-YbCl₃-HCl-H₂O water-salt system at 25°C along the (40 ± 0.2)% HCl section; this is a eutonic-type system. The composition of the eutonic solution is as follows (wt %): LaCl₃ · 7H₂O, 4.67, YbCl₃ · 6H₂O, 0.37; HCl, 37.98; and H₂O, 56.98.     

Phase diagram studies of methanol–CHF3 and methanol–H2O–CHF3 mixtures

Comprehensive phase diagrams of methanol/CHF₃ and methanol/H₂O/CHF₃ mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO₂ for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF₃ and methanol/H₂O/CHF₃ was compared to that of methanol/CO₂ and methanol/H₂O/CHF₃. Fluoroform is markedly more miscible with methanol or methanol/H₂O than is CO₂. Data for methanol/CHF₃ binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.     

A Thermodynamic Study of 1-Propanol–Glycerol–H2O at 25°C: Effect of Glycerol on Molecular Organization of H2O

The excess chemical potential, partial molar enthalpy, and volume of 1-propanol were determined in ternary mixtures of 1-propanol–glycerol–H₂O at 25°C. The mole fraction dependence of all these thermodynamic functions was used to elucidate the effect of glycerol on the molecular organization of H₂O. The glycerol molecules do not exert a hydrophobic effect on H₂O. Rather, the hydroxyl groups of glycerol, perhaps by forming clusters via its alkyl backbone with hydroxyl groups pointing outward, interact with H₂O so as to reduce the characteristics of liquid H₂O. The global hydrogen bond probability and, hence, the percolation nature of the hydrogen bond network is reduced. In addition, the degree of fluctuation inherent in liquid H₂O is reduced by glycerol perhaps by participating in the hydrogen bond network via OH groups. At infinite dilution, the pair interaction coefficients in enthalpy were evaluated and these data suggest a possibility that the interaction is mediated through H₂O.     

Liquid–Solid Phase Diagrams of PrOH–Water and BuOH–Water Systems from Differential Scanning Calorimetry

The freezing process in i-PrOH- and tert-BuOH-water systems were investigatedto obtain reliable liquid=nsolid phase diagrams by differential scanning calorimetry(DSC), especially focusing on formation of metastable solid phases. In addition,n-BuOH, sec-BuOH, and i-BuOH were studied within their solubility limits. Inmost systems studied, there exist metastable solid phases and, with increasingbranching of alkyl groups, the number of metstable solid phases increases. Themost complicated is i-PrOH-water where curious phenomena were found,probably because of the abnormally high viscosity of the solution at low temperatures.The relation between hydration in the liquid and formation of solid phases isdiscussed. It is suggested that the positional relation between methyl groups andalcoholic OH groups plays an important role; the increase in number ofalphamethyl group seems to strengthen hydration and stabilizes solid hydrates.     

Apparent Molar Volumes and Adiabatic Compressibilities of Crown Ethers and Glymes in H2O and D2O at 25°C

The apparent molar volumes and adiabatic compressibilities of 18-Crown-6, 15-Crown-5, 12-Crown-4, tetraglyme, and triglyme were measured at 25°C in H₂O and D₂O. The contribution of the -CH₂CH₂O- group to the limiting partial molar volumes and compressibilities of cyclic and open-chain ethers in both solvents are compared and solvent isotope effects calculated. It is concluded, based on the compressibility results, that there is a subtle difference between the hydration of the ethene oxde group in cyclic and open-chain ethers and that this difference persists in D₂O. These results indicate that the calculation of limiting apparent molar compressibilities using additivity schemes will have to account for whether the group is in a cyclic or open-chain compound.     

Heats of chemisorption ofn-Aliphatic alcohols on α-Al2O3 at 25–200°C

A differential microcalorimeter (E. Calvet) was used to study the processes of adsorption of five aliphatic alcohols (C₁-C₅) on α-Al₂O₃ at 25, 50, 100, 150 and 200°C. In particular, the importance of the thermokinetic study of the chemisorption of such alcohols at different experimental temperatures was demonstrated, with regard to the variations in the thermokinetic parameters (t_max, t_1/2 and t₀) and the evolution of the alcohol vapor pressure on the adsorbent during the adsorption process. It was concluded that:

1. all the heat emission peaks of alcohol adsorption have the same rounded shape at 25°C;
2. on passing from methanol to 1-pentanol, the area of the adsorption peaks increases as the chain length or molecular weight increases;
3. on passing from 25 to 200°C, the shape of the adsorption peaks becomes more pointed.

     

Experimental Study on Phase Equilibria in Na2B4O7–Na2SO4–H2O and Li2B4O7–Na2B4O7–H2O Aqueous Ternary Systems at 273 K

Russian Journal of Physical Chemistry A - The solubility data for ternary systems Na2SO4–Na2B4O7–H2O and Li2B4O7–Na2B4O7–H2O at 273 K were obtained experimentally by the...     

Hygrometric Determination of the Water Activities of the Aqueous Solutions of the Mixed Electrolyte NaCl–CaCl2–H2O at 25°C

The mixture {yNaCl + (1 – y)CaCl₂}(aq) has been studied with the hygrometric method at the temperature 25°C. The water activities were measured at total molalities from 0.25 mol-kg^–1 to near saturation for different ionic-strength fractions y of NaCl with y = 0.33, 0.50, and 0.67. The obtained data allow the calculation of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii–Stokes–Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LS II), Reilly–Wood–Robinson (RWR), and Pitzer models. From the measured osmotic coefficients, the Pitzer ionic mixing parameters _{Na Ca} and _{Na Ca} Cl are determined and are used to predict the solute activity coefficients in the mixtures. The excess Gibbs energy is also determined. These results are compared with those given in the literature.     

Phase diagram of an iodine-potassium iodide-water-ethanol system at 25°C

Phase equilibriums are studied in the isothermal-isobaric sections of the phase diagram of a fourcomponent iodine-potassium iodide-water-ethanol system at 25°C and atmospheric pressure. The compositions of the solvent at which it exhibits the greatest ability to dissolve iodine are established. It is shown that in all the investigated sections, there is three-phase eutonic equilibrium with potassium iodide and crystalline iodine as the solid phases. It is revealed that in the sections containing 30 and 50% of ethanol, potassium iodide serves as the salting in agent for crystalline iodine, due to the formation of polyiodide complexes of various composition in the studied system.     

Solubility Diagram of a Fullerenol-d-NaCl-H2O System at 25°C

Solubility in a ternary fullerenol-d-NaCl-H₂O system is studied at 25°C with the use of isothermal saturation. It is established that the solubility diagram is composed of two branches that are responsible for the crystallization of fullerenol-d crystallohydrate and anhydrous sodium chloride, and it contains one invariant eutonic-type point that corresponds to cosaturation by the above two solid phases. The so-called salting-out effect was observed on the branch of the crystallization of fullerenol-d, while salting in was observed on the branch of the crystallization of sodium chloride.     

Solubility and Crystallization in the System MgCl2–MgSO4–H2O at 50 and 75°C

The system MgCl₂–MgSO₄–H₂O has been investigated experimentally and modeled thermodynamically according to the Pitzer method at 50 and 75°C. It was found that, even when seemingly all requirements for reaching the stable thermodynamic equilibrium are fulfilled, the crystallization of higher hydrates as metastable phases is possible, and cannot be avoided in each crystallization field of a stable lower hydrate of magnesium sulfate. Crystallization of MgSO₄ · x H₂O (x = 1, 4, 6) and MgCl₂ · 6 H₂O at 50°C and of MgSO₄ · H₂O and MgCl₂ · 6 H₂O at 75°C as stable phases has been observed. Three metastable crystallization fields of MgSO₄ · x H₂O (x = 4, 6, 7) have been detected at 50°C and two of MgSO₄ · x H₂O (x = 4, 6) at 75°C. The results obtained and the contradictions existing in the literature with respect to the solubility and the crystallizing solid phases are discussed in terms of the crystal structures.     

Carbon-Supported Palladium–Gold Bimetallic Disperse Systems Formed in Aqueous Solutions at 110°С

Various palladium–carbon composites have been manufactured by autoclaving at 170°С to be used as precursors for manufacturing bimetallic particles. The morphology of the manufactured items was comprehensively studied by scanning electron microscopy; the ultrafine metal palladium was found to have particles sizes lying in the range 30–120 nm. The specifics of hydrothermal reduction of gold(III) chloro complexes by palladium–carbon composites at 110°С have been studied. An appreciable increase in gold(III) reduction rate was observed with the use of a palladium–carbon composite relative to the rate observed for ultrafine metallic palladium. Gold is reduced on a palladium–carbon composite to an individual metallic phase.     

Phase equilibria and salting-out effects in a cesium nitrate-triethylamine-water system at 5–25°C

Phase equilibria and critical phenomena in a cesium nitrate-water-triethylamine system in which the constituent binary liquid system is stratified at the lower critical solution temperature (LCST) is studied in a range of 5–25°C by the visual polythermal method. It is found that introducing cesium nitrate into the water-triethylamine system leads to a slight reduction in the LCST (from 18.3 to 16.3°C) and to a decrease in the mutual solubility of the components. The distribution coefficients of triethylamine between aqueous and the organic phases of the monotectic state at different temperatures are calculated. It is found that the salting-out of triethylamine from aqueous solutions by cesium nitrate increases with rising temperature. The results of the salting-out effect of sodium, potassium, and cesium nitrates on a water-triethylamine binary system are compared.     

Solubility of the Copper(II) Salt–Sodium Formate–Water Systems at 25°C

Solubilities in the CuSO₄ (CuCl₂, Cu(NO₃)₂)–NaHCOO–H₂O systems are studied at 25°C using the isothermal sections method. Crystallization regions of copper(II) formate mono- and dihydrate are elucidated. It is proved that copper(II) formate can be synthesized in CuAn₂ + 2NaHCOO ? Cu(HCOO)₂ + 2NaAn–H₂O quaternary reciprocal systems using the conversion method.     

Interaction in the nickel perchlorate–acetamide–perchloric acid–water system at 25°С

Heterogeneous equilibria in the nickel perchlorate–acetamide–perchloric acid–water quaternary system at 25°С were studied by studying solubility. The crystallization regions were determined for the initial solid components, eutonic compositions of the ternary systems constituting the quaternary system, binary compounds of acetamide with nickel perchlorate and perchloric acid, and also two new coordination compounds containing simultaneously nickel perchlorate, acetamide, and perchloric acid: Ni(ClO₄)₂ · 4CH₃CONH₂ · HClO₄ and Ni(ClO₄)₂ · 2CH₃CONH₂ · HClO₄.     

Interaction in the zinc perchlorate–urea–perchloric acid–water system at 25°С

Heterogeneous equilibria in the zinc perchlorate–urea–perchloric acid–water quaternary system at 25°С were studied by investigating solubility. The crystallization regions were found for the initial solid components, eutonic compositions of the ternary systems constituting the quaternary system, binary compounds of urea with zinc perchlorate and perchloric acid, and also two new coordination compounds containing simultaneously zinc perchlorate, urea, and perchloric acid: ZnClO₄ · 4CO(NH₂)₂ · HClO₄ and ZnClO₄ · 2CO(NH₂)₂ · HClO₄.     

Solid–liquid Equilibria in the Quaternary System Na+, Mg2+//Cl–, SO2–4–H2O at 25 and 30°C

The isoplethic sections in the diagram of the quaternary system Na⁺ , Mg²⁺ //Cl^– , SO^2– ₄ –H₂ O were established at 25 and 30oC by analytical and conductometric measurements. Three compounds can be observed in the isoplethic sections: NaCl, Na₂ SO₄ and MgNa₂ (SO₄ )₂ 4 H₂ O. Seven fields are determined, relating to the precipitation of one, two or three salts. The solubility range of MgNa₂ (SO₄ )₂ 4 H₂ O is wide, while the liquidus curve of Na₂ SO₄ is very short. The compositions, expressed in Jänecke coordinates, at the eutonic and peritonic points, respectively, were: 42.70% Cl^– and 745% H₂ O; 79.47% Cl^– and 787% H₂ O; 71.6% Cl^– and 744% H₂ O at 25°C; and 48.80% Cl^– and 715% H₂ O; 80.20% Cl^– and 778% H₂ O; 70.14% Cl^– and 707% H₂ O at 30°C.