Volumetric properties of itaconic acid aqueous solutions

Densities of itaconic acid aqueous solutions were measured at 5 K intervals from T = (278.15 to 343.15) K. From the determined densities, the apparent molar volumes, the cubic expansion coefficients and the second derivatives of volume with respect to temperature which are interrelated with the derivatives of isobaric heat capacities with respect to pressure were evaluated. These derivatives were qualitatively correlated with the changes in the structure of water when itaconic acid is dissolved in it.     

Volumetric properties of aqueous solutions of quinic acid and its sodium salt

Abstract  

The apparent molar volume of quinic acid and its sodium salt were determined from the density data of aqueous solutions up to molality of 0.4 mol kg⁻¹ and in the temperature range from 293.15 to 328.15 K. The apparent molar volume of sodium quinate comprises the ionic and the associated ion-pair contributions. From the apparent molar volumes of quinic acid and the quinate ion, the molecular contributions to that of quinic acid are derived. At 298.15 K, the limiting apparent molar volume of quinic acid is 119.8 ± 0.5 cm³ mol⁻¹, and that of the quinic ion is 111.6 ± 0.3 cm³ mol⁻¹. Similarly, at 298.15 K, the limiting apparent molar expansibility of sodium quinate is 0.198 ± 0.003 cm³ mol⁻¹ K⁻¹, and that of quinic acid is 0.142 ± 0.003 cm³ mol⁻¹ K⁻¹. From these limiting ionic and molecular apparent molar volumes, the limiting volume change caused by ionization of quinic acid was calculated as −8.2 cm³ mol⁻¹ at 298.15 K. The coefficients of thermal expansion of these solutions were calculated from the density data, and from these the apparent molar expansibilities of quinic acid and its sodium salt were derived.     

Volumetric properties of sodium perfluoroalkylcarboxylates in aqueous solutions at different temperatures

Densities and sound velocities of sodium perfluorohexanoate and sodium perfluorononanoate for different concentrations above and below the critical micelle concentration (cmc) have been obtained at different temperatures. Apparent molar volumes and compressibilities of the surfactants in the monomeric and micellar form have been estimated. The relevant results were plotted as a function of the temperature and the alkyl chain length by using previous data reported for sodium heptanoate and sodium octanoate. The expected linear behaviour in function of temperature and also alkyl chain length have been found. In order to analyze the influence of the substitution of the hydrogen by fluorine in the alkyl chain of the surfactant, the data were compared with the hydrogenated counterpart.     

Volumetric properties of dilute aqueous solutions of poly(ethylene glycols)

The densities of aqueous solutions of some poly(ethylene glycols) (mono-, di-, tri-, and tetraethylene glycol, and four carbowaxes with a mean molecular weight ranging from 600 to 15,000), and of di-, tri-, and tetraethylene glycol dimethyl ether have been determined at 25°C, in the concentration range 5–100 g/liter. From these data, the limiting partial specific and/or molar volume of the solute has been calculated. A value of 37.0 ml/monomole has been evaluated for the partial molar volume of the repeating unit ? CH₂CH₂O? , and has been found independent of both terminal groups and chain length. The results suggest that the ethylene units in higher polymers are accessible to the solvent as easily as in oligomers, and support an “open” or extended conformation of the poly(ethylene glycol) chain in aqueous dilute solution. This interpretation has been confirmed by a comparison of the experimental values of partial molar volume with the values calculated by semiempirical models.     

Volumetric properties of aqueous solutions of amino acids from the singular to critical temperature

The partial volume -V ₂ ⁰ of amino acids in aqueous solution is assumed to be zero for T = 227 K (singular temperature) and T= T _c (critical temperature). The literature data for -V ₂ ⁰(T) of ten amino acids at 278–328 K are reproduced by the two-parameter equation with a standard deviation of 0.06–0.16 cm³/mol. Only for asparagine and tryptophan the standard deviation exceeds 0.3 cm³/mol. In the case of glycine and alanine, the relation -V ₂ ⁰(T) in the high temperature range is obtained. -V ₂ ⁰ is divided into contributions (?-H ₂ ⁰/?p) _T and —T·(?-S ₂ ⁰/?p) _T . Their dependence on the temperature and amino acid nature is discussed. Positive values of ?-C ₂ ⁰/?p) _T characterize amino acids as water structure breakers; however, the differentiation of compounds by this feature is not successful. The behavior of amino acids in aqueous solutions is compared with the behavior of urea.     

Volumetric properties of glucose in aqueous HCl solutions at temperatures from 278.15 to 318.15 K

Densities have been measured for Glucose + HCl +Water at 10-degree intervals from 278.15 to 318.15 K. The apparent molar volumes (V _Φ,G) and standard partial molar volumes (V _Φ,G ⁰ ) for Glucose in aqueous solution of 0.2, 0.4, 0.7, 1.1, 1.6, 2.1 mol·kg⁻¹ HCl have been calculated as well as volumetric interaction parameters (V _EG) for Glucose — HCl in water and standard partial molar expansion coefficients (∂V _Φ,G ⁰ / ∂T)_p. Results show that (1) the apparent molar volume for Glucose in aqueous HCl solutions increases lineally with increasing molality of Glucose and HCl; (2) V _Φ,G/0 for Glucose in aqueous HCl solutions increases lineally with increasing molality of HCl; (3) the volumetric interaction parameters for Glucose — HCl pair in water are small positive and vary slightly with temperature; (4) the relation between V _Φ,G ⁰ and temperature exists as V _Φ,G ⁰ = a ₀ + a ₁(T − 273.15 K)^2/3; (5) values of (∂V _Φ,G ⁰ / ∂T)_p are positive and increase as temperatures rise, and at given temperatures decrease slightly with increasing molalities of HCl, indicating that the hydration of glucose decreases with increasing temperature and molality of HCl. These phenomena are interpreted successfully by the structure interaction model. Translated from Acta Chimica Sinica, 2006, 64(16): 1635–1641 (in Chinese)     

Volumetric properties, structural effects, and hydration of amino acids in aqueous salt solutions

The dependence of the standard partial volumes of glycine, α-alanine, and serine on the ionic strength of aqueous sodium chloride and sulfate solutions is modeled by the extended Masson equation: {ie534-1}. The error of less than 0.2 cm³/mol is a result of using five values of the A and B parameters: the two values of A are determined by the type of salt and the three values of B by the type of amino acid. A new variation of the additive-group approach is proposed for {ie534-2}. The partial volumes of the CH₃ group (α-alanine) and the CH₂ group (serine) are found not to depend on the salt concentration. The partial volume of the CH₂ group of glycine grows with concentration. The structural characteristics of the hydrated complexes of the NH ₃ ⁺ and COO^? groups are calculated: the hydration numbers, the molar volumes of water inside and outside the hydration sphere, and the intrinsic volume of NH ₃ ⁺ in COO^? in solution. Given the same ionic strength, the aqueous sodium sulfate solution produces a somewhat stronger dehydration of the charged groups.     

Physicochemical properties of aqueous solutions of L-aspartic acid containing chitosan

Physicochemical properties of aqueous solutions of L-aspartic acid with and without addition of chitosan have been studied by conductometry, potentiometry, refractometry, tensiometry, and viscosimetry. It has been shown that aspartic acid molecules take a cyclic configuration stabilized by hydrogen bonds in aqueous solution at c > 0.04 g/dL (298 K). The interaction of chitosan with aspartic acid results in the formation of the polymeric salt that dissociates in aqueous solution to give chitosan polycation [~(NH₃)⁺] and aspartate counterions. The addition of chitosan to solutions of L-aspartic acid results in progressive increase in the surface tension, absorbance, and refractive index as well as the change in hydrodynamic properties of the macromolecules. The polymeric salt exhibits polyelectrolyte properties in dilute aqueous solutions. The increase in temperature impairs the thermodynamic quality of the solvent for chitosan leading to the shrinkage of the polymer coils and, hence, to the decrease in the intrinsic viscosity of the system.     

Acid-base properties and stability of sulfoxylic acid in aqueous solutions

A comparative study of decomposition of sulfoxylic acid S(OH) ₂ and sulfoxylate anion and their reactions with formaldehyde in aqueous solutions with different acidity was carried out. Using the obtained results, the pK ₁ value of S(OH) ₂ was determined for the first time.     

Surface properties of aqueous solutions of trifluoroacetic and acetic acid mixture

The coadsorption of trifluoroacetic and acetic acid at the free surface of water was investigated. Knowing the composition of mixed monolayer and the effective dipole moments of individual molecules, the surface potential was calculated. The synergetic effect of the surface properties of mixed adsorbed films was observed.     

Volumetric properties of dilute aqueous solutions of cobalt-amine-type salts. Part I. Densities at 25°C

The densities of dilute aqueous solutions of [CoL₃]X₃ [L=1,2-diaminoethane(en), 1,2-diaminopropane(pn), 1,3-diaminopropane(tn) X=Cl^–, Br^– and (ClO₄)^–] have been measured at 25°C from 0 to 5×10^–2m. The apparent molar volumes were calculated and extrapolated to infinite dilution. Ion-solvent interactions were detected from the change of the ionic partial molar volumes with concentration. These interactions depend both on the properties of the ion (polarization charge density at the surface, hydrophobic groups, etc.) and the characteristics and structure of the solvent.     

Diffusion in polyacrylic acid aqueous solutions

The four diffusion coefficients for the ternary system polyacrylic acid (mol. weight 5000)-polyacrylic acid (mol. weight 115000)-water have been measured at 25°C and at one average polyelectrolytes concentration. The experimental values of main and cross terms have been briefly discussed. The large cross term D ₁₂ in the system with water as solvent shows that, contrary to intuition, different molecular weight species do interact with each other.     

Radiolysis of aqueous solutions of nitrilotriacetic acid

The radiolysis of nitrilotriacetic acid (NTA) in neutral or alkaline solution, was studied in the presence and in the absence of dissolved oxygen. The radolytic yields of decomposition of NTA and formation of iminodiacetic acid(IDA) were determined; G(-NTA) was found to be equal to G(IDA). The formation of hydrogen peroxide and carbonyl compounds was also followed. The radiolysis was found to be initiated by hydrogen abstraction by both H and OH radicals with the formation of a dehydrogenated radical intermediate which ultimately stabilizes to give products. The radiolytic mechanism under different conditions has been discussed. From competition kinetic studies with sodium formate in neutral solution, the rate constant, k(OH + NTA), was found to be 3.0 x 10⁸ dm³ mol⁻¹s⁻¹.