Liquid–liquid and liquid–liquid–solid equilibrium in Na2CO3–PEG–H2O

The phase diagram was determined for the Na₂CO₃–PEG–H₂O system at 25°C using PEG (poly(ethylene glycol)) with a molecular weight of 4000. Compositions of the liquid–liquid and the liquid–liquid–solid equilibria were determined using calibration curves of density and index of refraction of the solutions, and atomic absorption (AA) and X-ray diffraction analyses were made on the solids. The solid phase in equilibrium with the biphasic region was Na₂CO₃·H₂O. Binodal curves were described using a three-parameter equation. Tie lines were described using the Othmer–Tobias and Bancroft correlation’s. Correlation coefficients for all equations exceeded 0.99. The effects of temperature (25 and 40°C) and the molecular weight of the PEG (2000, 3000, and 4000) on the binodal curve were also studied, and it was observed that the size of the biphasic region increased slightly with an increase in these variables.     

Isoamyl­cobalamin–acetone–water (1/0.385/12.650)

The title compound, [Co(C₅H₁₁)(C₆₂H₈₈N₁₃O₁₄P)]·0.385C₃H₆O·12.650H₂O, contains the isoamyl (3‐methyl­butyl) anion bonded to the Co^III ion through a C atom. The compound is thus a structural analog of the two biologically important vitamin B₁₂ coenzymes adenosyl­cobalamin and methyl­cobalamin. The lower axial Co—N bond length [2.277 (2) Å] is one of the longest ever reported for a cobalamin and reflects the strong σ‐donor ability of the isoamyl group.     

Diiso­propyl­phosphitocobalamin–acetone–water (1/3.48/7.56)

The di­iso­propyl­phosphite ligand in the title diiso­propyl­phosphitocobalamin compound, [Co(C₆₈H₁₀₂N₁₃O₁₇P₂)]·3.48C₃H₆O·7.56H₂O, coordinates to the Co^III atom via its P atom. The crystal structure is isomorphous with that of other cobalamins that adopt packing type II [Gruber, Jogl, Klintschar & Kratky (1998). Vitamin B₁₂ and B₁₂ Proteins, edited by Kräutler, Arigoni & Golding, pp. 335–347. New York: Wiley–VCH], with a Co—P bond length [2.227 (1) Å] similar to that found in other phosphitocobalamins. The structural trans influence in cobalamins is discussed.     

Phase transitions and azeotropic properties of acetic acid–n-propanol–water–n-propyl acetate system

The brief review of the data on VLE and LLE in acetic acid–n-propanol–water–n-propyl acetate system is presented. The azeotropic properties and the topological structure of the residue curve map at 313.15 K are discussed. This system is one of the few reacting systems with an extensive set of data on binary and ternary subsystems, in chemically nonequilibrium states. The main aim of the paper is to present the set of combined data that could be helpful for the development of thermodynamics of the systems with chemical reactions, and for modeling of coupled phase and reactive equilibria.     

Poly(styrene–b–ethylene/butylene–b–styrene)/cobalt ferrite magnetic nanocomposites

Magnetic nanoparticles were created in or around the sulfonated (s) polystyrene domains in a poly[styrene–b–(ethylene–co–butylene)–b–styrene)] block copolymer (BCP) using an in situ inorganic precipitation procedure. The sBCP was neutralized with a mixed iron/cobalt chloride electrolyte, and the doped samples were converted to their oxides by reaction with sodium hydroxide. Transmission electron microscopy indicated the presence of nanoparticles having diameters of 20–50 nm. Metal oxide particle structures were studied using wide angle X–ray diffraction, which revealed that they were inverse spinel cobalt iron oxide crystals. Thermogravimetric analysis provided the weight percent of the inorganic component and nanocomposite thermal decomposition profile. Modulated differential scanning calorimetry studies suggested that the inorganic inclusions were selectively grown in the polystyrene hard block phase. These nanocomposites were shown, using alternating gradient magnetometry, to be ferrimagnetic at room temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1475–1485, 2005     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

Leurosine me­thio­dide–methanol–water (1/3/2)

The crystal structure of a methanol–water solvate ofleurosine me­thio­dide, (leurosine‐CH₃)⁺I^?·3CH₃OH·2H₂O (C₄₇H₅₉IN₄O₉·3CH₃OH·2H₂O), is described. The piperidine ring of the upper part of the mol­ecule adopts a sofa conformation. An intramolecular hydrogen bond between the tertiary N and the hydroxyl group of the vindoline moiety of the mol­ecule is present.     

2‐Aminopyridinium–succinate–succinic acid (2/1/1)

In the title compound, 2C₅H₇N₂⁺·C₄H₄O₄^2?·C₄H₆O₄, cyclic eight‐membered hydrogen‐bonded rings exist involving 2‐amino­pyridinium and succinate ions. The succinic acid and succinate moieties lie on inversion centres. Succinic acid mol­ecules and succinate ions are linked into zigzag chains by O—H?O hydrogen bonds, with O?O distances of 2.6005 (16) Å.     

Effect of TiO2 addition on the crystallization and tribological properties of MgO–CaO–SiO2–P2O5–F glasses

The kinetic parameters including the activation energy for crystallization (E), the Avrami parameter (n) and frequency factor (υ) of a glass in the MgO–CaO–SiO₂–P₂O₅–F system were studied using non-isothermal differential thermal analysis (DTA) with regard to small amount of TiO₂ additions. It has been shown that the role of TiO₂ changes from a glass network former to a glass network modifier with increasing TiO₂ content in this system. The kinetic parameters of the crystallizing phases, apatite and wollastonite, indicated changes accompanied with TiO₂ additions, implying that the TiO₂ is an effective nucleating agent for promoting the crystallization of apatite and wollastonite. The most effective addition is of about 4 wt% TiO₂ in this system. The wear rate and friction coefficient decreased from 1.8 ± 0.1 to 0.9 ± 0.2 and 0.87 to 0.77, respectively, when 4 wt% TiO₂ was incorporated to the base glass.     

2‐Amino­pyridinium–fumarate–fumaric acid (2/1/1)

The title complex, 2C₅H₇N₂⁺·C₄H₂O₄²⁻·C₄H₄O₄, contains cyclic eight‐membered hydrogen‐bonded rings involving 2‐­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H⋯O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen‐bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H⋯O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.     

Magnesium iodide–4,4′‐bipyridine–water (1/3/4) and strontium iodide–4,4′‐bipyridine–propan‐1‐ol (1/2.5/2)

Both of the title compounds, catena‐poly­[[[tetra­aqua­magnesium(I)]‐μ‐4,4′‐bi­pyridine‐κ²N:N′] diiodide bis(4,4′‐bi­pyridine) solvate], {[Mg(C₁₀H₈N₂)(H₂O)₄]I₂·2C₁₀H₈N₂}_n, (I), and catena‐poly­[[[μ‐4,4′‐bi­pyridine‐bis­[di­iodo­bis­(propan‐1‐ol)­strontium(I)]]‐di‐μ‐4,4′‐bi­pyridine‐κ⁴N:N′] bis(4,4′‐bi­pyri­dine) solvate], {[Sr₂I₄(C₁₀H₈N₂)₃(C₃H₈O)₄]·2C₁₀H₈N₂}_n, (II), are one‐dimensional polymers which are single‐ and double‐stranded, respectively, the metal atoms being linked by the 4,4′‐bi­pyridine moieties. The Mg complex, (I), is [cis‐{(H₂O)₄Mg(N‐4,4′‐bi­pyridine‐N′)_(2/2)}]_(∞|∞)I₂·4,4′‐bi­pyridine and Mg has a six‐coordinate quasi‐octahedral coordination environment. The Sr complex, (II), is isomorphous with its previously defined Ba counterpart [Kepert, Waters & White (1996). Aust. J. Chem. 49 , 117–135], being [(propan‐1‐ol)₂I₂Sr(N‐4,4′‐bi­pyridine‐N′)_(3/2)]_(∞|∞)·4,4′‐bi­pyridine, with the I atoms trans‐axial in a seven‐coordinate pentagonal–bipyramidal Sr environment.     

Hexa­methyl­enetetra­mine–4‐nitro­catechol–water (1/2/1)

In the title adduct, 1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]dec­ane–4‐nitro­benzene‐1,2‐diol–water (1/2/1), C₆H₁₂N₄·2C₆H₅NO₄·H₂O, the hexa­methyl­ene­tetra­mine mol­ecule acts as an acceptor of intermolecular O—H?N hydrogen‐bonding interactions from the water mol­ecule and the hydroxy groups of one of the two symmetry‐independent 4‐nitro­catechol mol­ecules. The structure is built from molecular layers which are stabilized by three intermolecular O—H?O, two intermolecular O—H?N and four intermolecular C—H?O hydrogen bonds. The layers are further interconnected by one additional intermolecular O—H?N and two intermolecular C—H?O hydrogen bonds.     

Felodipine–diazabicyclo[2.2.2]octane–water (1/1/1)

The title compound, C₁₈H₁₉Cl₂NO₄·C₆H₁₂N₂·H₂O, is a cocrystal hydrate containing the active pharmaceutical ingredient felodipine and diazabicyclo[2.2.2]octane (DABCO). The DABCO and water molecules are linked through O—H...N hydrogen bonds into chains around 2₁ screw axes, while the felodipine molecules form N—H...O hydrogen bonds to the water molecules. The felodipine molecules adopt centrosymmetric back‐to‐back arrangements that are similar to those present in all of its four reported polymorphs. The dichlorophenyl rings also form π‐stacking interactions. The inclusion of water molecules in the cocrystal, rather than formation of N—H...N hydrogen bonds between felodipine and DABCO, may be associated with steric hindrance that would arise between DABCO and the methyl groups of felodipine if they were directly involved in hydrogen bonding.     

Hydro­gen bonding in calcium–tri­fluoro­methane­sulfonate–1,3‐di‐4‐pyridyl­urea–methanol (1/2/2/4)

The structure of the supramolecular complex calcium–tri­fluoro­methane­sulfonate–1,3‐di‐4‐pyridyl­urea–methanol (1/2/2/4), Ca²⁺·2CF₃SO₃⁻·2C₁₁H₁₀N₄O·4CH₄O, is presented. The Ca²⁺ ion lies on an inversion centre and is octahedrally coordinated by four methanol mol­ecules and two tri­fluoro­methane­sulfonate counter‐ions. The molecular packing is dominated by hydrogen‐bonded sheets in the (110) plane which contain R(32) rings; in these rings, significant π–π interactions are observed between inversion‐related 1,3‐di‐4‐pyridyl­urea mol­ecules.     

Solid–liquid phase equilibrium in the systems of LiBr–H2O and LiCl–H2O

A set of empirical temperature-molar fraction expressions for solid–liquid equilibrium curves of LiBr–H₂O and LiCl–H₂O systems is presented. The expressions are based upon a body of experimental data that have been compiled and critically evaluated. The equations cover the full composition range for LiCl–H₂O system and compositions up to the salt mole fraction of x = 0.46 (i.e. mass fraction of w=0.805) for LiBr–H₂O, corresponding to transition from monohydrate to anhydrate. Temperatures and solution compositions at the eutectic point and at transition points between hydrates have been determined from intersections of the curves corresponding to the adjacent hydrate ranges of the phase diagram. Equations of a special structure were used, involving the coordinates of the transition points as parameters, which makes possible their direct non-linear optimization. To obtain more reliable results, a procedure was employed optimizing both the temperature–composition and composition–temperature equations simultaneously. The uncertainty in the obtained values of the transition point coordinates are estimated to be of the order of 1 K for temperature and 0.001 for the composition expressed in salt mole fraction. Gaps in the database are shown to give experimenters orientation for future research.