Liquid–liquid phase equilibria of the ternary system of water/TBA/2-ethyl-1-hexanol

Liquid–liquid phase equilibria (LLE) for the system of water/tert-butyl alcohol (TBA)/2-ethyl-1-hexanol were investigated experimentally at different temperatures of 298.15, 303.15, 308.15, and 313.15 K. A type 1 liquid–liquid phase diagram was obtained for this ternary system. These results were correlated simultaneously by the UNIQUAC model. The values of the interaction parameters between each pair of components in the system were obtained for the UNIQUAC model using the experimental results. The root mean square deviation (RMSD) between the observed and calculated mole percents was 2.58%. The mutual solubility of 2-ethyl-1-hexanol and water was also investigated by the addition of TBA at different temperatures.     

Clay—water interactions and the mechanism of soil swelling

The examination of micropore structure in swollen systems such as wet clay soils must be preceded by removal of the enmeshed water. For such mechanically weak systems the drying process used to remove this water is of the utmost importance. This paper discusses the problem in connection with the elucidation of soil swelling mechanisms.The pore size distributions of compressed cores and natural aggregates of a clay soil have been measured over the range 2 nm–50 μm for samples which have been rapidly frozen and freeze-dried from a wide range of water potentials. These results are discussed in relation to an earlier proposal that the swelling of divalent clay systems results from the water-initiated release of stresses, accumulated as particle distortion during drying and leads to the formation of discontinuities in the soil fabric in which water is retained by surface tension forces. The observation of pores in the 1-μm range is thought to be largely an artifact from the freeze-drying process. A preliminary result based on solvent exchange and critical point drying suggests that this drying method may give a more reliable indication of the pore structure of the swollen soil.     

Phase equilibria in binary subsystems of urea–biuret–water system

Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the fusion enthalpy and temperature determination of the biuret (NH₂CO)₂NH (synthesis by-product of the urea fertilizer (NH₂)₂CO). Recommended values are Δ_m H = (26.1 ± 0.5) kJ mol⁻¹, T _m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested.     

Synthesis and swelling behavior of temperature responsive κ-carrageenan nanogels

Crosslinked κ-carrageenan hydrogel nanoparticles (nanogels) with an average size smaller than 100 nm were prepared using reverse microemulsions combined with thermally induced gelation. The size of the nanogels varied with biopolymer concentration at a constant water/surfactant concentration ratio. The nanogels were found to be thermo-sensitive in a temperature range acceptable for living cells (37-45°C) undergoing reversible volume transitions in response to thermal stimuli. This opens the possibility to explore the application of these nanogels in smart therapeutics such as thermo-sensitive drug carriers. As such, the sustained release of methylene blue from the nanogels was evaluated in in vitro conditions as proof of concept experiments and the release rate was found to be controlled with temperature.     

Phase diagram of the water–monoethanolamine system

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Phase and extraction equilibria in the water—ethoxylated nonylphenol—sodium sulfate system

Russian Chemical Bulletin - Phase equilibria in the water-ethoxylated nonylphenol (neonol AF 9–12)-sodium sulfate system were studied at 25 °C using isothermal titration and isothermal...     

Liquid–liquid equilibria for the ternary system water + tetradecane + 2-butyloxyethanol

Liquid–liquid equilibria of the ternary system water + tetradecane + 2-butyloxyethanol in the temperature range from 298.15 to 338.15 K were investigated at atmospheric pressure. The experimental data correlated well with the UNIQUAC model. For the system with a three-liquid-phase-coexisting region, all the six UNIQUAC interaction parameters can be determined numerically by minimizing the deviation of the compositions of three coexisting liquid phases only.     

Phase equilibria in the aluminium-rich side of the Al–Zr system

The Al-rich phase equilibria in the Al–Zr binary system were investigated experimentally. The phase diagram for compositions up to 40 at.% Zr was determined experimentally by differential thermal analysis and metallography. Three stable intermetallic compounds exist in this region of the diagram: Al₃Zr₂, Al₂Zr, and Al₃Zr. The peritectic melting of Al₃Zr₂ and the congruent melting of Al₂Zr were confirmed. Al₃Zr, the most Al-rich intermetallic compound, melts peritectically, which contradicts information available in the literature. In addition, the reaction between Al₃Zr and the (Al) solid solution seems to be of eutectic nature, in contradiction with previous results found in the literature. Based on these new experimental evidence, a revised phase diagram is drawn.     

Liquid—liquid equilibria of the system water + acetic acid + methyl ethyl ketone at several temperatures

This article reports the solubilities and equilibrium data of the ternary mixture water + acetic acid + methyl ethyl ketone at 25, 35 and 45°C, and the equilibrium data of the binary system water + methyl ethyl ketone over the range 20–55°C. NRTL and UNIQUAC equations have been fitted to the experimental data for the ternary system, which are also compared with the values predicted by the UNIFAC method.     

Critical properties of the vapor—liquid equilibria of the binary system acetone—n-pentane

Hajjar, R.F., Cherry, R.H. and Kay, W.B., 1986. Critical properties of the vapor—liquid equilibria of the binary system acetone—n-pentane. Fluid Phase Equilibria, 25: 137–146.The P—V—T—x properties for the acetone—n-pentane azeotrope-forming system have been measured by the technique developed by Kay. The experimental uncertainties have been estimated at 0.05 K, 2.4 kPa and 0.06% of the volume. The results for eight different compositions covering the range 180 to 200°C and 2.5 to 4.0 MPa are given. Smoothed critical loci have been plotted. The critical temperatures and pressures were correlated by a quadratic relationship of the form Q_cm = Σ_iΣ_jx_ix_jQ_cij where i, j = 1, 2. The maximum discrepancy in the critical temperature was 0.6 K and in the critical pressure was 0.012 MPa.     

Phase equilibria and critical phenomena in the cesium nitrate–water–pyridine ternary system

The solubilities of components, phase equilibria, and critical phenomena in the cesium nitrate–water–pyridine ternary system are studied in the 5–100°C temperature range by the visual–polythermal method. Cesium nitrate is found to exhibit a salting-out effect at temperatures above 79.9°C causing phase separation in homogeneous water–pyridine solutions. The temperature of formation of the critical monotectic tie line (79.9°C) and the compositions of solutions corresponding to the liquid–liquid critical points at three temperatures are determined. The pyridine distribution coefficients between the aqueous and organic phases of the monotectic state at 85.0, 90.0, and 100.0°C are calculated. Their values demonstrate that salting-out of pyridine from aqueous solutions by cesium nitrate increases at higher temperatures. The plotted isotherms of phase diagrams confirm the fragment of the scheme of topological transformation of the phase diagrams of salt–binary solvent ternary systems with salting-in and salting-out phenomena.     

Mechanism and kinetics of the production of hydroxymethyl hydroperoxide in ethene/ozone/water gas-phase system

The mechanism and kinetics of the production of hydroxymethyl hydroperoxide (HMHP) in ethene/ ozone/water gas-phase system were investigated at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The reactants were monitored in situ by long path FTIR spectroscopy. Peroxides were measured by an HPLC post-column fluorescence technique after sampling with a cold trap. The rate constants (k3) of reaction CH2O2 H2O→HMHP (R3) determined by fitting model calculations to ex-perimental data range from (1.6―6.0)×10?17 cm3·molecule?1·s?1. Moreover, a theoretical study of reac-tion (R3) was performed using density functional theory at QCISD(T)/6-311 (2d,2p)//B3LYP/6-311 G(2d, 2p) level of theory. Based on the calculation of the reaction potential energy surface and intrinsic reac-tion coordinates, the classic transitional state theory (TST) derived k3 (kTST), canonical variational tran-sition state theory (CVT) derived k3 (kCVT), and the corrected kCVT with small-curvature tunneling (kCVT/SCT) were calculated using Polyrate Version 8.02 program to be 2.47×10-17, 2.47×10-17 and 5.22×10-17 cm3·molecule-1·s-1, respectively, generally in agreement with those fitted by the model.     

Liquid–liquid equilibria of water/acetic acid/1-butanol system — effects of sodium (potassium) chloride and correlations

Sodium and potassium chloride were experimentally shown to be effective in modifying the liquid–liquid equilibrium (LLE) of water/acetic acid/1-butanol system in favour of the solvent extraction of acetic acid from an aqueous solution with 1-butanol, particularly at high salt concentrations. Both the salts enlarged the area of the two-phase region; decreased the mutual solubilities of water and marginally decreased the concentrations of 1-butanol and acetic acid in the aqueous phase while significantly increased the concentrations of the same components in the organic phase. These effects essentially increased the heterogeneity of the system, which is an important consideration in designing a solvent extraction process. The equilibrium data were well correlated by Eisen–Joffe equation with respect to the overall molar ratio of salt to water in the liquid phases. By expressing the salt–solvent interaction parameters as a third order polynomial of salt concentration in the liquid phase, Tan's modified NRTL model [T.C. Tan, Trans. Inst. Chem. Eng., Part A 68 (1990) 93–103.] for solvent mixtures containing salts or dissolved non-volatile solutes was able to provide good correlation of the present LLE data. Using the regressed salt concentration coefficients for the salt–solvent interaction parameters and the solvent–solvent interaction parameters obtained from the same system without salt, the calculated phase equilibria compared satisfactorily well with the experimental data.     

Interaction of sodium and potassium ions withκ-carrageenan

Summary NMR and potentiometric methods revealed at least two types of interactions of Na⁺ and K⁺ ions with -carrageenan, viz., Coulombic interaction with polysaccharide sulfate groups, and a coordination one, leading, in the case of the Na⁺ ions, to formation of nonstoichiometric complexes. The absence of any correlation between the coordination binding density of the cations and their promoting effect on gelation process was demonstrated.     

The association and complexation equilibria in the system D-glucitol—nickel(II)—water

A joint study using polarimetry, spectrophotometry, and mathematical modeling revealed the formation of 1: 1, 2: 1, and 4: 4 outer-sphere complexes of nickel(II) ions with neutral D-glucitol (H₆Glc-ol), viz., {[Ni(H₂O)_n]?(H₆Glc-ol)aq}₂+, {[Ni(H₂O)_n]₂?(H₆Glc-ol)aq}⁴⁺, and {[Ni(H₂O)_n]₄?[(H₆Glc-ol)aq]₄}⁸⁺ in a weakly acidic medium. In aqueous solutions, D-glucitol forms tetramers. For each form, the constant of formation and the specific optical rotation was calculated.     

Thermodynamic characteristics and phase equilibria in the alloys of the Ge–La system

Mixing enthalpies of melts of the Ge–La system have been measured using isoperibolic calorimetry within two concentration ranges. For the first range (0 < x _La < 0.16 at 1520 K and 0.16 < x _La < 0.29 at 1570 K), agreement with the known literature data is observed within the experimental error. The second range (0.78 < x _La < 1 at 1470 K and 0.7 < x _La < 0.78 at 1580 K) has been studied for the first time. The melts are characterized by very strong exothermal effects of mixing, which have almost symmetrical concentration dependence: ΔH? _La ^∞ = ΔH? _Ge ^∞ = ?245 kJ/mol at 1470 K. A thermodynamic optimization of the activities of the components and the phase diagram of the system have been conducted based on the obtained experimental data, using an ideal associated solution (IAS) model.     

Separation of microamounts of yttrium from strontium in the two‐phase water/nitrobenzene system

A rapid and very effective separation of carrierfree 90 Y in the aqueous phase of the water/nitrobenzene system from an 90 Y/90 Sr generator is proposed. After a twostage extraction separation, the radionuclide impurity of 90 Sr in the final aqueous phase containing carrierfree 90 Y is approximately 10 16%, while the chemical yield of 90 Y in this phase is practically 100%.     

Concentration dependences of the physicochemical properties of a water–acetone system

Concentration dependences of the UV spectrum, refractive index, specific electrical conductivity, boiling point, pH, surface tension, and heats of dissolution of a water–acetone system on the amount of acetone in the water are studied. It is found that the reversible protolytic interaction of the components occurs in all such solutions, resulting in the formation of hydroxyl and acetonium ions. It is shown that shifts of the equilibrium between the molecules and ions in the solution leads to extreme changes in their electrical properties. It is concluded that the formation of acetone solutions of water is accompanied by heat absorption, while the formation of aqueous solutions of acetone is accompanied by heat release.     

High pressure vapour–liquid equilibria for the mixture dl-γ-tocopherol/methanol

dl-γ-Tocopherol is one of the four homologues compounds also known as vitamin E. Tocopherols are present in all four forms (α-, β-, γ-, δ-tocopherol) in many natural sources and extraction design of purification processes used for their enrichment needs detailed knowledge of the phase equilibrium behaviour. Experimental vapour–liquid equilibrium data (pressure–composition isotherms) for the binary system dl-γ-tocopherol/methanol at four temperatures 473 K, 498 K, 523 K, 543 K and pressures up to 12 MPa are presented. The measurements were carried out in a static constant volume high-pressure apparatus. Different cubic equations of state and mixing rules were used to model the data. A modified Redlich–Kwong–Soave EOS gives the better correlation. On the basis of the new experimental data and those for the system dl-α-tocopherol/methanol and reasonable agreement between the two systems, using for both the same thermodynamic model, behaviour of the ternary system dl-α-tocopherol/dl-γ-tocopherol/methanol has been predicted.