Determination of hexafluoropropan-2,2-diol in its binary mixtures with water

A visual titration method for the determination of hexafluoropropan-2,2-diol (HFPD) in HFPD-water mixtures is suggested. The procedure involves the titration of the weakly acidic HFPD with sodium methoxide, using dimethylformamide or ethanol as solvent and thymol blue as indicator. The results are in good agreement with the ones obtained by potentiometric titration in water.     

Solid—liquid phase diagrams of mixtures containing substituted phenols and amine mixtures

The thermal decomposition of CaCO₃ was studied under high vacuum by means of both TG and the more recently developed constant decomposition rate thermal analysis (CRTA) which allows the monitoring of both reaction rate and the residual pressure over the sample. The reliability of the kinetic results seems to be much higher with the latter technique which actually allows the reduction of the reaction rate and therefore the heat and mass transfer effects over a broad range of sample size. For instance, it was necessary, by conventional TG started under a vacuum of 2 10^?6 torr with a heating rate of 0.5 K min^?1, to lower the amount of sample to 2 mg in order to obtain the same activation energy as that calculated from CRTA with various samples weighing up to 50 mg. The TG experimental conditions quoted above (and which are upper limits of mass and heating rate) are beyond the limit of sensitivity of most available conventional TG equipment.     

Analytical applications of liquid-liquid phase equilibria: analysis of binary mixtures of chemically similar components

A new, simple and rapid method based on the principle of liquid-liquid phase equilibria has been developed for the analysis of binary mixtures of chemically similar organic compounds. The method does not require elaborate instrumentation and can be used to analyse mixtures of members of homologous series. The application of the method has been illustrated by analysing binary mixtures of n-hexane and n-octane; the maximum uncertainty in this analysis is ~2%.     

Osmotic coefficients of polystyrenesulphonates in dioxane-water mixtures—II. Divalent counterions and mixtures of mono- and divalent counterions

The osmotic pressures of solutions of magnesium and calcium polystyrenesulphonate in water and in 25 wt % mixture of dioxane in water have been measured for concentrations from 0?002 to 0?06 molal in monomer units. The osmotic coefficient derived from these measurements is almost independent of concentration. Its values for solutions in dioxane-water mixtures are much lower than for aqueous solutions. The osmotic coefficients of solutions containing mixtures of polystyrenesulphonic acid and its calcium salt in 25 wt % dioxane have also been determined. The osmotic coefficient of these solutions has a distinct maximum at a certain value of the equivalent fraction of the acid. The experimental results are compared with the predictions of the cylindrical cell model and infinite line charge model. Satisfactory agreement between theory and experiment is found.     

Thermodynamic studies of some binary mixtures containing a self-associated component. II. Excess volumes of some mixtures of tetrahydrofuran with alcohols

Excess volumes of mixing, V^E, for binary mixtures of tetrahydrofuran (THF) with methanol, ethanol, n-butanol, tert-butanol, 2-bromoethanol and ethylene glycol have been determined from the experimental density measurements at 298.15 K over the entire composition range. The V^E data follow the order: ethylene glycol < 2-bromoethanol < methanol < ethanol < n-butanol < tert-butanol. The results have been explained in terms of self-association and the hydrogen bond-donating abilities of alcohols.     

Thermodynamics of solvent extraction of thorium by solutions of HHTA and mixtures of HHTA and TBP

The changes in free energy, enthalpy and entropy for the extraction of thorium by solutions of thenoyltrifluoroacetone (HTTA) and mixtures of solutions of HTTA and tri-n-butylphosphate (TBP), in three diluents, viz. cyclohexane, benzene and chloroform, were determined using the solvent extraction data obtained at different temperatures. From these data the thermodynamic parameters associated with the formation of Th(TTA)₄ · TBP in the respective organic diluents were evaluated. Trends in the enthalpy changes were attributed to different degrees of association of the diluents with themselves and with the solutes present in them.     

Thermodynamics of associated mixtures of the Mecke—Kempter type

A chain-forming associated solution theory based on the UNIQUAC equation is presented for alcohol-unassociated active component liquid mixtures of the Mecke—Kempter type. The capability of the theory in reproducing the excess Gibbs free energy and excess enthalpy data for many binary mixtures is successfully shown. Ternary extension of the theory is presented in the calculations of vapor—liquid and liquid—liquid equilibria and excess enthalpy data from binary data.     

Topological aspects of the thermodynamics of binary mixtures of non-electrolytes

An approach based on the “graph” theory has been evolved to predict molar excess enthalpies, H^E, and molar excess volumes, V^E, for a number of binary mixtures of non-electrolytes. The calculated H^E and V^E values compare reasonably well with their corresponding experimental values. The limitations of this approach have also been discussed.     

Polarography of 4-nitrodiphenylamine (DPA) in methanol-water mixtures

The polarographic reduction of 4-nitro DPA in methanol-water mixtures of varying composition (30–80% v/v) in the pH range 1–12 was investigated. A single wave was observed in the reduction in these media at all pH values and solvent compositions. The number of electrons involved in the reduction was found to be six in all solutions indicating that 4-amino DPA is the final product. A mechanism consistent with these observations which involves the formation of 4-hydroxylaminodiphenylamine as an intermediate has been proposed.     

Application of the principle of congruence to ternary alkane mixtures

Excess enthalpies and excess volumes at 298.15 K and atmospheric pressure have been measured for mixtures of n-hexane + (an equimolar mixture of n-tridecane + n-nonadecane). The agreement of the results with the corresponding results for mixtures of n-hexane + n-hexadecane is interpreted as confirmation of the applicability of the principle of congruence to multicomponent mixtures.     

Thermodynamic and transport properties of binary liquid acid—base mixtures. Part 1

Densities and viscosities were determined at five different temperatures for the systems quinoline (Q) with: phenol (P); ortho-chlorophenol (CP); and meta-cresol (MC). From the experimental results the excess volumes, excess viscosities, partial molar excess volumes and the partial molar volumes were calculated. From the dependency of viscosity on temperature, the thermodynamic parameters of activation of flow were also calculated and these results were discussed in terms of the type of interaction between the two components in solution.     

Thermodynamics of complex formation in ternary liquid mixtures containing acetonitrile

Vapor—liquid and liquid—liquid equilibria and excess enthalpies for ternary mixtures formed from acetonitrile, benzene, n-heptane, toluene, and carbon tetrachloride are successfully correlated with a modified version of the associated solution theory proposed by Lorimer and Jones in 1977, which assumes two types of self-association for acetonitrile and binary complexes between acetonitrile and unsaturated hydrocarbons and does not include any ternary parameters.     

Heat capacities and volumes of interaction between mixtures of alcohols in water at 298.15 K

The heat capacities and densities of mixtures of aqueous solutions of normal alcohols (methanol to n-butanol) and t-butanol were measured at 298.15 K at low molalities. The results were used to calculate the thermodynamic pair and triplet interaction parameters between solutes for heat capacities and volumes. The pair parameters are approximately a linear function of the total number of carbon atoms of the two solutes. The enthalpic pair and triplet interaction parameters for (ROH + H₂O) are also reported. The temperature dependence of the pair parameters for Gibbs free energies, enthalpies, entropies, heat capacities, and volumes are discussed in terms of structural changes in the aqueous solutions.     

Osmotic coefficients of polystyrenesulphonates in dioxane-water mixtures—I Monovalent counterions

The osmotic pressures of solutions of polystyrenesulphonic acid and its alkali salts in water, and in 25 and 50 wt% mixtures of dioxane in water have been measured for concentrations from about 0-001 to 0–03 M in monomer units. The osmotic coefficient derived from these measurements decreases with decreasing dielectric constant of the solvent and increases slowly with increasing concentration of the polyelectrolyte. By comparing the experimental results with the predictions of the cylindrical cell model and infinite line charge model, satisfactory agreement between theory and experiment has been obtained.     

Thermodynamics of molecular interactions in binary mixtures of non-electrolytes. Molar excess volumes

Molar excess volumes, V^E, for pyridine (A) + α-picoline (B), + β-picoline (B) and + γ-picoline (B) and benzene (A) + toluene (B), + o-xylene (B) and + p-xylene (B) and carbon tetrachloride (A) + n-heptane (B) have been measured dilatometrically as a function of temperature and composition and have been utilized to study B—B and B—B—B interactions in the presence of A via the Mayer—McMillan approach. A model has also been presented to account for these B—B and B—B—B interactions. The V^E data at 308.15 K have also been analysed in terms of the “graph theoretical” approach which describes the V^E data well for all these mixtures at 308.15 K. The “graph theoretical” approach has further been extended to successfully evaluate V^E data for a mixture at any temperature, T₂, when the V^E data at T₁ are known.     

Irreversible cathodic behavior of graphite in the presence of some mixtures of onium salts

The electrochemically induced dissolution of ferrocene in a carbon paste electrode is investigated by using chronoamperometry at constant potential. Two types of behaviour are observed, according to the initial form of ferrocene: particles or deposit. The experimental i-t curves are respectively in agreement with the theoretical curves, derived earlier, in the case of spherical particles or planar slabs of solid. The analysis of the curve shows that the process is diffusion controlled, so that the dissolution rate of ferrocene cannot be measured. The parameters calculated from the curves (thickness of the deposit, initial distance from the electrode, area) have a reasonable order of magnitude.     

Excess volumes,enthalpies, and Gibbs free energies for mixtures of benzene + p-xylene

Excess thermodynamic properties of benzene + p-xylene have been obtained at 288.15, 298.15, and 313.15 K. V^E was obtained with a Sodev vibrating-tube densimeter, H^E with a Picker flow microcalorimeter, and G^E was calculated from solid + liquid phase equilibria measurements. Measurements were also made of the heat capacity of liquid p-xylene as a function of temperature using the heat-capacity unit of the Picker flow microcalorimeter.     

The thermodynamic properties of binary mixtures containing carbon disulphide I. Phase diagrams and excess volumes

Phase diagrams and excess volumes at 298.15 K have been measured for the four binary mixtures carbon disulphide+cyclohexane, +n-hexane, +1,5-hexadiene, and +1,5-hexadiyne. The results are discussed qualitatively in the light of recent theoretical calculations of the structure and thermodynamic properties of mixtures containing anisotropic molecules.