Solubility Polytherms Research Articles

Thermodynamic Description of Liquid Crystalline N(p-n-Alkyloxybenzyliden)-p’-Toluidines with Organic Solvents

Solubility polytherms of nematic (smectic-nematic) N(p-n-alkyloxybenzyliden)-p’-toluidenes (n-alkyl = C4H9, C9H19, C10H21) in organic solvents have been studied. Thermal analysis, visual-polythermal and solubility methods were used. The solution enthalpies of these mesogens in 8 solvents (n-hexane, n-heptane, benzene, p-xylene, cyclohexane, methylcyclohexane, ethanol, n-propanol) were determined. To calculate the solubility polytherms, thermodynamic methods based on the Hildebrand solubility parameters were used. The advantage of the proposed calculation method is that it requires a minimum of experimental parameters (fusion enthalpy and melting temperature of pure mesogen) and the data obtained from the structural formula (group contribution increments) of a mesogen to evaluate its solubility polytherms.

Calculations of solubility polytherms of phosphate salts in their mixtures with ammonium chloride and optimization of conditions for selective crystallization of ammonium orthophosphates

The purpose of the work was to determine the optimal conditions for preparation of chemically pure salts of ammonium orthophosphates based on solutions formed after purification of extractable orthophosphoric acid from toxic impurities of d-metals, lead, arsenic and fluorine by their coprecipitation with calcium hydrogen phosphate. Based on the Sechenov's modified formula, a method for calculating the solubility polytherms of orthophosphate salts in their mixtures with ammonium chloride was proposed. For its experimental confirmation, studies were conducted to determine the concentrations of saturated solutions of a number of orthophosphate salts in their mixtures with ammonium chloride at temperatures of 14, 40 and 800C. The results of the calculations were well confirmed by experiments on selective crystallization. It was shown that the following chemically pure products can be obtained from solutions of mixtures of (NH4)2HPO4 and NH4Cl by the methods of isothermal-isohydric crystallization: (NH4)2HPO4 (with a yield of up to 79.5%) and NH4H2PO4 (with a yield of up to 52.4%). Measurements of the concentrations of Cd(II), As(III), Cu(II), Pb(II) and fluorine in the synthesized salts showed that they were at levels lower than the current requirements for maximum permissible concentrations. Therefore, these salts can be recommended for use as food additives.

Phase equilibria in 4-pentyloxybenzoic acid - long-chain <i>n</i>-alkane systems

Objective. The work’s objective is to develop methods for the thermodynamic modeling of systems of liquid crystal - organic solvent. Methods. Four binary systems of nematic 4-pentyloxybenzoic acid (5OBA) with n-alkanes (hexadecane, octadecane, icosane, and docosane) were investigated via thermal analysis methods (differential thermal analysis, polarization microscopy, visual polythermal analysis, and the polytherm solubility method). The accuracy in determining phase transitions temperatures is within 0.3 K. To describe the phase equilibria, models based on the Hildebrand and Hansen solubility parameters were used. Hansen solubility parameters were estimated using the Stefanis scheme. Hildebrand solubility parameters, molar volumes, and vaporization enthalpies were calculated using a group contribution scheme. Results. Phase equilibria in the systems of 5OBA with n-alkanes were studied. Four T-x diagrams were obtained by thermal analysis methods, coordinates of invariant points (eutectics and metatectics) were determined in the systems. A linear dependence of the metatectic coordinate ( х 1 is a fraction of 5OBA, mol. %) on the number of C atoms in the alkane (N) was established: x 1 = -0.3131 x N + 85.467. Solubility polytherms of 5OBA with solvents of different polarity were obtained: n-alkanes (hexane, octane), cyclohexane, aromatic compounds (benzene, toluene, and o-xylene), chlorobenzene, ethyl acetate, acetone, 1,4-dioxane, alcohols (propan-2-ol, propan-1-ol, butan-1-ol), and acetonitrile. The dependence of 5OBA’s solubility on the difference in the solubility parameters of the components and the distance Ra was established. Conclusions. The model for regular solutions based on solubility parameters allows us to calculate the solubility polytherms of mesogens and to select solvents for the purification of mesogens by the mass crystallization method. The best solubility of 4-pentyloxybenzoic acid at 298 K appears in chlorobenzene.

Solid Liquid Equilibria Studies in the KVO3–KNO3–H2O System in the Temperature Range 293.15–323.15 K

Mutual solubility of potassium metavanadate and potassium nitrate(V) was investigated in the KVO3–KNO3–H2O system at the temperature range 293.15–323.15 K. The equilibrium studies were conducted using isothermal saturation of a solution method. On the base of the received results, a fragment of the solubility polytherm for the investigated system was plotted. The knowledge of the course of that isotherm for the ternary system is necessary to plot the equilibrium diagram in a planar projection prepared according to the Janecke method for the systems of exchange salts NH4NO3–KVO3–H2O and to determine optimal conditions for utilization of the postfiltration liquor from soda production with the soda–chlorine–saltpeter method.

Mobile nanostructures (cybotactic groups) as a basis of generalised phenomenological model of aqueous electrolyte solutions

In this paper, we briefly review our researches into concentrated electrolyte solutions by means of a proposed phenomenological model. Electrolyte solutions are complex systems with a multitude of interactions. However, totality of interactions in solution is reflected in its constitution. The description of solution structure includes all parameters that define short-range ordering of particles, a full description of all possible coexistent vibrationally averaged structures (V-structures). We believe that information about the presence of the concentration ranges with different dominant structures and boundaries may be derived from the solubility polytherm (phase diagram) of the water-salt system. The boundary concentration corresponds to the eutectic composition (EC). In the range of pre-eutectic concentrations the dominant structure is the proper structure of water, and ion hydration is the major type of interaction between components. A crystalline hydrate or anhydrous salt crystallises at reduced temperatures from solutions with post-eutectic concentrations; hence, the dominant solute included V-structures are the structures of corresponding crystalline hydrate or quasi-crystalline fragments of anhydrous salt. For above-discussed spatial ordering of particles we used Stewart's term 'cybotactic group' (CG), which is a nanodimensional mobile V-structure that corresponds to the unit cell of a solid phase, which crystallises from solution under freezing. Analysis of concentration dependences of structural-sensitive properties (parameters) serve as information source about structural changes in solution, and 'special points' or singularities as the concentration boundaries of structural changes in solution correspond to eutectic and peritectics on solubility diagram. We proposed a new method of sounding to probe some peculiarities and differences in the solution structure. This method consists of monitoring of structural and dynamical features of new micro components introduced into the system under investigation. As such micro components one can use small additives of salts of transition and rare-earth metals. The structure of solution has a pronounced effect on the condition of complex-forming cations, which are presented as additives. If dominant structure (CG) has changed, there are alterations in structural and dynamical parameters of micro components, thus indicating that their behaviour 'obeys' the overall structural rearrangement in the solution. Such alterations of micro components can serve for probing some differences in the dominant structure of the supporting solution.

Phase Equilibria in Triacylglycerols – Ethanol – Oleic Acid – Athyl Oleate Quasi-Quaternary System

<p>In order to use waste vegetable oils to produce biodiesel a possibility of reagents (sunflower oil and ethanol) mixture homogenization under the simultaneous effect of two cosolvents (oleic acid and ethyl oleate) was investigated. The possibility of action of oleic acid and ethyl oleate as cosolvents was analyzed with GSP model. For qualitative assessment of the intermolecular interaction parameter ξ was used. This parameter is a measure <br />of the ratio between cross-association (solvation) energy A–B and self-association (association) energies A–A and B–B. It was shown that most important role at intermolecular interactions of oleic acid and ethyl oleate with triglycerides belonged to dispersion forces. Predominant contribution of hydrogen bonds in the interaction of oleic acid and ethyl oleate with ethanol was shown. The prediction of improving the effect of the cosolvents with temperature increasing was done, and it was confirmed by experimental results.<br />The effect of oleic acid and ethyl oleate as cosolvents for homogenization of mixtures of sunflower oil and ethanol was investigated experimentally by studying the phase equilibria in the quasi-quaternary system triacylglycerols (sunflower oil) –ethanol –oleic acid –ethyl oleate at 30, 40, 50, 60 and 70 °C. The results of the experiments are presented in the form of phase diagrams of quasi-ternary boundary systems: triacylglycerols –oleic acid –ethanol and triacylglycerols –ethyl oleate –ethanol, and the phase <br />diagrams of composition tetrahedron sections with five different ratios of components oleic acid: ethyl oleate. Generalization of the research results is presented in the form of polythermal phase diagram for the system triacylglycerols –ethanol –oleic acid –ethyl oleate. Solubility polytherms (from 30 to 70 °C) for the system triacylglycerols –ethanol –mixed cosolvent with different ratios of oleic acid and ethyl oleate were plotted.</p>

Solubility polytherms and eutectic concentrations of scandium, yttrium, and lanthanum perchlorate solutions

Freezing points of solutions M(ClO4)3-H2O (M = Sc, Y, La) of different concentrations were determined. The solubility polytherms of the perchlorate systems studied, as well as aluminum, gallium, and indium perchlorates were compared with the concentration dependences of different properties of the corresponding solutions. Viscometry and IR spectroscopy allowed the special points on these dependences to be correlated with eutectic concentrations. Structural changes in the systems studied as a function of solute concentration were described.

Solubility of aluminum, gallium, and indium perchlorates in water

Solubility polytherms of the system M(ClO4)3-H2O (M3+ = Al3+, Ga3+, In3+) were measured. Positions of singular points and vitrification ranges were determined. Values of eutectic concentrations were compared with earlier known data on the inversion concentrations measured by the viscometry method. Compositions of found crystalline hydrates were calculated from the solubility polytherms. The concept of the ability of the studied aqua cations to show properties of aqua acids, of the structure of solutions of posteutectic concentrations (structurally forced processes and microheterogeneity), of the electronic structure of M3+ cations, and of the localized hydrolysis phenomenon were used to understand the existence of the polyaqua compounds.

Solubility of light fullerenes in oleic, linoleic, and linolenic acids at 20–80°C

Solubility of light fullerenes (C60, C70, and the standard fullerene mixture containing (wt %): C60 65, C70 34, Cn>70 1) in the oleic, linoleic and linolenic acids, respectively, at 20–80°C was studied and the corresponding solubility polytherms were reported.

Solubility of bromine derivatives of C60Br n fullerene in α-chloro- and α-bromonaphthalene in the temperature range 10–60°C

Isothermal saturation in ampoules was used to study the solubility of bromine derivatives of fullerene C60Brn (n = 6, 8, 24) in α-C10H7Cl and α-C10H7Br in the temperature range of 10–60°C. The corresponding solubility polytherms were characterized, and the compositions of the equilibrium crystal solvates and the density of the saturated solutions of C60Brn were determined.

Solubility of light fullerenes in vegetable oils

Polythermal (in the temperature range 0−80°C) solubility of light fullerenes (C60 and C70), and also of fullerene mixtures (65% C60, 34% C70, and 1% C76–90) in vegetable oils (of unrefined and refined sunflower, corn, olive, linen, apricot, grape, cedar, and walnut) was studied; the corresponding solubility polytherms are given and characterized.

Solubility of Light Fullerenes in Styrene

This Article presents data on the solubility of fullerenes in binary C60 + C6H5CH═CH2 and C70 + C6H5CH═CH2 systems within the temperature range from (15 to 80) °C and the solubility of fullerenes along with their distribution between liquid and solid phases in the ternary C60 + C70 +C6H5CH═CH2 system at temperatures of (−15, 0, and 25) °C. The solubility polytherms for the said binary systems and isotherms for the said ternary system are discussed; compositions of equilibrium solid phases are determined.

Solubility polytherm and the influence of temperature on the enthalpy and entropy of dissolution

The significance and metrological meaning of parameters accessible to regressive estimates from the experimental data on solubility polytherms are refined using corollaries to the universal interrelation between the Gibbs energy, enthalpy, and entropy of dissolution. A standard procedure for processing solubility polytherms is suggested. Its informativeness is illustrated for the example of new metrologically verified data on the polytherm of solubility of ferrocene in pure water.

The solubility of C60Br n (n = 6, 8, 24) in organic solvents

The polythermal (over the temperature range 20–80°C) solubility of fullerene bromo derivatives C60Brn (n = 6, 8, 24) in several solvents (o-xylene, o-dichlorobenzene, n-decanol-1, and enanthic acid) was studied. The corresponding solubility polytherms are given.

The solubility of light fullerenes in styrene over the temperature range 20–80°C

The temperature dependence (over the range 20–80°C) of the solubility of light fullerenes (C60 and C70) and a mixture of fullerenes (60 wt % C60, 39 wt % C70, and 1 wt % C76–90) in styrene was studied. The corresponding solubility polytherms are given and characterized.

Structural microheterogeneites in strontium perchlorate solutions of posteutectic concentrations

Aqueous solutions of strontium perchlorate were studied in a wide range of concentrations at room temperature by X-ray diffraction, thermogravimetry, and calorimetry. The features of the solubility polytherm of strontium perchlorate, that distinguish it from those of other Group II metal perchlorates, were explained in terms of two coexisting interconverting crystal hydrates.

The solubility of fullerenes in butyric and enanthic acids at 20–80 °C

The polythermal solubility of C60 and fullerene mixture (60% C60, 39% C70, and 1% C76–90) in butyric and enanthic acids was studied over the temperature range 20–80 °C. The corresponding solubility polytherms are given and characterized.

Solubility in the NH4NO3 + NaNO3 + H2O System

The mutual solubility of salts in the ternary system NH4NO3 + NaNO3 + H2O was investigated in the temperature range 293−323 K by the method of isothermal saturation of solutions. The data obtained were used for plotting the section of the solubility polytherm for the system investigated. Knowledge of the course of the solubility polytherm is necessary for developing a new method of utilization of the post-filtration lye from the soda−chlorine−saltpeter method (SCS) of soda production.

Utilization of the post-filtration lye from the SCS method of soda production

Utilization of the post-filtration lye from the SCS method of soda production The mutual solubility of salts in the NaVO3-NaNO3-H2O system was investigated at 293 - 323 K temperature range by the method of isothermal saturation of solutions. A fragment of the solubility polytherm for that system was plotted, based on the obtained data. The investigated system is a part of the quaternary NH4NO3-NaVO3-NH4VO3-NaNO3 system, and it is necessary for plotting the solubility isotherm as a planar projection according to Janecke, since it defines one edge of its square. Knowledge of the isotherm for that quaternary system is necessary to determine the optimal utilization conditions for the post-filtration lye, formed during the soda production from NaNO3 by the Solvay method, using NaVO3.

Polythermal study of the solubility of fullerenes in pelargonic and caprylic acids

A polythermal study of the solubility of C60 and a fullerene mixture (60% C60 + 39% C70 + 1% C76–C90) in pelargonic and caprylic acids was carried out at 20–80°C. The solubility polytherms are given and discussed.