The solubility of disperse dyes in an aqueous sodium dodecyl sulfate solution

Summary The solubilities of the following compounds in an aqueous sodium dodecyl sulfate solution were determined at 25°, 30°, 35° and 40°C: biphenyl, azobenzene, p-chloroazobenzene, p-aminoazobenzene, p-N,N-dimethylaminoazobenzene and p-nitroazobenzene. From the results the thermodynamic parameters for the transfer of the model compounds from water to SDS micellar environment were calculated. The resulting thermodynamic parameters were not so certain, but suggested that with biphenyl, azobenzene and p-chloroazobenzene which seem to be solubilized in the SDS micellar interior the solubilizing process is a result of a favourable increase in entropy, and that with p-aminoazobenzene, p-N, N-dimethylaminoazobenzene and p-nitroazobenzene which seem to be solubilized in the SDS micellar surface the solubilizing process is a result of a favourable decrease in enthalpy. The favourable increase in entropy was explained in terms of iceberg and the favourable decrease in enthalpy in terms of interfacial energy.     

The solubilities of azobenzene derivatives in water

Summary The solubilities of azobenzene derivatives in water have been determined at 5 °C intervals from 0° to 40 °C to obtain the information both about the effect of polar groups on the solubility of aromatic compounds in water and about the action of polar groups to the iceberg-formation in the vicinity of hydrophobic part of the solute in water environment. From the results the imaginary super cooled pure liquid has been taken as a standard state and the thermodynamic parameters of solution of azobenzene derivatives in water have been calculated.     

Enthalpies and heat capacities of transfer of sodium carboxylates and sodium dodecylsulfate from water to aqueoustert-butyl alcohol solutions

Integral enthalpies of solution at very low concentrations of sodium carboxylates and sodium dodecylsulfate in aqueous tert-butyl alcohol solutions at 25°C and 35°C were measured with an isoperibol submarine calorimeter. The enthalpies and heat capacities of transfer of these surfactants from water to aqueous tertbutyl alcohol solutions were derived from integral enthalpies of solution. The results are explained in terms of the structural alteration effect of the constituent hydrophobic and hydrophilic groups of the solute.     

Enthalpies of solution in sodium octanoate + water + alcohol mixtures

Enthalpies of solution of sodium octanoate in water, 1-propanol and aqueous mixtures of 1-propanol, 1-butanol, 1-pentanol and 1-hexanol, and of the alcohols in aqueous solutions of sodium octanoate at various concentrations were determined calorimetrically at 35 °C. MostH(soln) values are exothermic and strongly dependent on the solute concentration. The main energetic factor governing the process of dissolution of the surfactant is associated with changes in the water structure caused by the presence of alcohol. That governing the process of the alcohol dissolution in surfactant solutions is due to the effect alcohols have on the CMC of the octanoate. There is no indication of the alcohol being either solubilized in the interior of the aqueous micelle, or becoming part of the micellar film.The solubility at 35 °C of sodium octanoate in water, 1-propanol and their mixtures has also been determined.     

Acrylamide plasma-induced polymerization onto expanded poly(tetrafluoroethylene) membrane for aqueous alcohol mixture vapor permeation separation

To improve the vapor permeation performance of aqueous alcohol mixtures, acrylamide (AAm) plasma activation then post-graft polymerization onto an expanded poly(tetrafluoroethylene) (e-PTFE) membrane, e-PTFE-g-AAm, was synthesized in this study. The surface properties of the e-PTFE-g-AAm membrane were characterized using ATR/FTIR, SEM, AFM and the water surface contact angle. The degree of grafting increases with increasing polymerization temperature. A maximum value was obtained at 80 °C. The water contact angle of the pristine e-PTFE membrane and the e-PTFE-g-AAm membrane with a 21% grafting degree was 109.7° and 34.1°, respectively. Optimum vapor permeation performance was obtained using an e-PTFE-g-AAm membrane with a 21% grafting degree for a 90 wt.% aqueous ethanol solution, giving a permeate water concentration of 99.4% and a permeation rate of 648 g/m² h.     

Thermosensitive poly(methyl methacrylate) emulsion prepared in the presence of poly(vinyl alcohol) with a cloud point as a protective colloid

An emulsion of poly(methyl methacrylate) (PMMA) was prepared using poly(vinyl alcohol) (PVA) of low degree of hydrolysis with a cloud point as a protective colloid. The behaviour of an aqueous solution of PVA with 80% degree of hydrolysis was first investigated in terms of the Huggins constant in viscometry. MMA was polymerized using the PVA at 20 °C, where no abnormality in the aqueous PVA was observed. The change in transmittance of the emulsion observed with a UV–vis photometer revealed that in the case of UV light of wavelength 370 nm, the transmittance decreased markedly at around 30 °C with an increase in temperature, and then increased with a decrease in temperature. The thermosensitive property resulted from PVA with a low degree of hydrolysis with a cloud point, at a higher temperature of which the PVA loses solubility in water owing to weakening of the hydrogen bond between PVA molecules and water.     

A Volumetric Study of Water–Decyltrimethylanimonium Bromide–Pentanol Ternary System from 25 to 130°C at 2 and 19 MPa

Density measurements on decyltrimethylammonium bromide (DeTAB)–water and pentanol (PentOH)–DeTAB–water systems as functions of both alcohol and surfactant m _S concentrations were carried out at 2 and 19 MPa from 25 to 130°C. From experimental data for the water–DeTAB binary system, the standard (infinite dilution) partial molar volumes, expansibilities, and compressibilities of DeTAB, and the corresponding properties in the micellar phase are calculated. The trends of the standard partial molar volumes of PentOH V _R ^o in DeTAB micellar solutions as functions of m _S reflect the transfer of PentOH from the aqueous to the micellar phase, except at 130°C and 19 MPa. On the basis of an equation previously used, the distribution constant of PentOH between the aqueous and the micellar phases and the standard partial molar volume of alcohol in the aqueous and the micellar phases are obtained from V _R ^o data. Comparisons with data for PentOH in dodecyltrimethylammonium bromide are made.     

Water-alcohol interactions in the two-phase system water-alcohol-alkane

The system water-alcohol-alkane has been studied at 25°C as a possible model system for micelles. The solubility of water in pure alcohols and in octane in the presence of alcohol has been determined. The data suggest that water may enter the octane phase hydrogen bonded to the hydroxyl group of the alcohol. If this system has any bearing on aqueous micellar solutions, it seems possible that solubilized alcohol molecules may carry water into the micellar interior. Addition of 1,2-propanediol does not increase the water content in octane, probably because dimerization of the diol in octane is energetically more favorable than diol-water interactions.     

Salting-Out of <Emphasis Type="Italic">n</Emphasis>-Propyl Alcohol with Potassium Nitrate from Aqueous Solutions

The solubility of components and critical phenomena in the ternary system constituted by potassium nitrate, water, and n-propyl alcohol were studied by the visual polythermal method in the temperature range 25–80°C. The temperature of formaiton of the critical node of the monotectic equilibrium (critical solution-solid phase) and the solution compositions corresponding to the critical solution points at different temperatures were determined. The isothermal solubility diagrams of the system were constructed and the distribution coefficients of n-propyl alcohol at different temperatures were calculated. A comparative analysis of the salting-out effect exerted by potassium nitrate on aqueous solutions of n-propyl alcohol and isopropyl alcohol was done.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 398–402.Original Russian Text Copyright © 2005 by Sinegubova, Cherkasov, Il’in.     

Coupled tracer diffusion coefficients of solubilizates in ionic micelle solutions from liquid chromatography

The peak-broadening (Taylor dispersion) method is used to measure the diffusion of traces of alcohols (ethanol, n-butanol, n-hexanol, n-octanol, n-decanol) in aqueous solutions of sodium dodecylsulfate micelles at 25°C. A small quantity of each alcohol is injected into a long capillary tube containing a laminar stream of the micelle solution. The tracer diffusion coefficient is calculated from the broadened distribution of the eluted alcohol which is measured by differential refractometry. The fraction of each alcohol that is solubilized by the micelles is estimated from the drop in the diffusion coefficient relative to the value for the free alcohol molecules in pure water. The refractive index profiles across the dispersed samples are analyzed to obtain the cross-diffusion coefficient which gives the coupled flow of sodium dodecylsulfate produced by the tracer diffusion of each alcohol.     

Thermodynamics of association for benzene-benzyl alcohol,benzene-phenethyl alcohol,and fluorobenzene-benzyl alcohol in dilute aqueous solution

Vapor pressure measurements have been made on dilute aqueous solutions of benzene-benzyl alcohol (BZOH), benzene-phenethyl alcohol (PEOH), and fluorobenzene-BZOH at 15, 25, 35, and 45°C. The benzene results have been interpreted with a mass action model which attributes deviations from ideality to the formation of benzene dimers and heterodimers with BZOH and PEOH. The benzene heterodimers form endothermically at 25°C with large and negative heat capacity changes. The dimerization constant for the benzene-BZOH dimer reaches a maximum of 0.57 M^–1 at about 37°C, while the benzene-PEOH dimer reaches a maximum of 0.60 M^–1 around 30°C. The fluorobenzene results have been interpreted with a mass action model which, in addition to fluorobenzene dimers and heterodimers, includes the formation of a fluorobenzene-BZOH trimer. Thermodynamic properties for these aggregates are reported and compared with results obtained in previous studies.     

Thermal stability of solid and aqueous solutions of humic acid

The effects of temperature on the stability of a soil humic acid were studied in the present work. Solid samples of Gohy-573 humic acid (HA) and dissolved ones in aqueous solution (pH 6.0, 0.1 mol L⁻¹ NaClO₄) were investigated in order to understand the impact of temperature on the chemical properties of the material. The methods applied to solid samples in the present investigation were thermogravimetric analysis (TGA), temperature-programmed desorption coupled with mass spectrometry (TPD-MS), and in situ diffuse reflectance infrared Fourier transformed spectroscopy (in situ DRIFTS). Humic acid samples were studied in the 25-800 °C range, with focus on thermal/chemical processes up to 250 °C. The reversibility of the changes observed was investigated by cyclic changes to specified temperature ranges (40-110 °C). All measurements were conducted under inert-gas atmosphere in order to avoid samples combustion at increased temperatures. Aqueous solutions were analyzed by UV-vis absorption spectroscopy after storage at temperatures up to 95 °C, and storage times up to 1 week. For temperatures below 100 °C experiments on solid and aqueous samples have shown results which were consistent to each other. The amount of water desorbed is temperature dependent and up to 70 °C this process was totally reversible. Above 70 °C an irreversible loss of water was also observed, which according to UV-vis spectroscopy corresponds to water produced by condensation leading to more condensed polyaromatic structures. The water released up to 110 °C was about 7 wt% of the total mass of the dried humic acid, where less than 50% corresponded to reversibly adsorbed water. At higher temperatures (>110 °C), gradual decomposition resulting in the formation of carbon dioxide (110-240 °C), and carbon monoxide (140-240 °C) takes place. Hence, thermal treatment of Gohy-573 humic acid above 70 °C results in irreversible structural changes, that could affect chemical properties (e.g., complex formation) of the material.     

Preparation and Characterization of Titania Thin Films from Aqueous Solutions

Dip- or spin-coating and characterization of titania (TiO₂) thin films from various aqueous solutions have been studied. The aqueous titanium solutions mainly used in this study were halogen- and chelate-free solutions with the concentrations up to 1.4 M derived from titanium isopropoxide (TIP) with tetramethylammonium hydroxide (TMAOH) or some alkylamines, while aqueous and alcoholic solutions containing titanium atoms stabilized chelating ligands were examined for comparison. The TiO₂ films prepared from the TIP-TMAOH solution were already crystallized at 350°C to anatase form and those formed at 600°C had high transparency and refractive indices of 2.40. No carbon residue in the film prepared at 400°C was detected by XPS. The pure anatase form was sustained up to 850°C. Interestingly, it was found that the (004) preferentially oriented anatase films were obtained from TIP-lactic acid (LA) system until 700°C. The solutions containing citric acid (CA) or alkanolamines yielded anatase and rutile form fired at the temperatures equal to or higher than 600°C. Carbon residue was detected in the film fired at 400°C. The film thickness monotonically decreased from the upper to the bottom ends of the substrate. However, it was found that the thickness uniformity was drastically improved by an addition of sucrose to the aqueous solutions. The effects of the solution composition and polyhydroxy compounds on the crystal modifications of formed films and the film uniformity are discussed.     

Pervaporation separation of water-acetic acid mixtures through poly(vinyl alcohol) membranes crosslinked with glutaraldehyde

Poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by a solution method for the pervaporation separation of acetic acid-water mixtures. In the solution method, dry PVA films were crosslinked by immersion for 2 days at 40°C in reaction solutions which contained different contents of GA, acetone and a catalyst, HCl. In order to fabricate the crosslinked PVA membranes which were stable in aqueous solutions, acetone was used as reaction medium in stead of aqueous inorganic salt solutions which have been commonly used in reaction solution for PVA crosslinking reaction. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of GA was characterized by IR spectroscopy. Swelling measurements were carried out in both water and acetic acid to investigate the swelling behavior of the membranes. The swelling behaviour of a membrane fabricated at different GA content in a reaction solution was dependent on crosslinking density and chemical functional groups created as a result of the reaction between PVA and GA, such as the acetal group, ether linkage and unreacted pendent aldehydes in PVA. The pervaporation separation of acetic acid-water mixtures was performed over a range of 70–90 wt% acetic acid in the feed at temperatures varying from 35 to 50°C to examine the separation performances of the PVA membranes. Permeation behaviour through the membranes was analyzed by using pervaporation activation energies which had been calculated from the Arrhenius plots of permeation rates.     

Heat capacity of alcohols in aqueous solutions in the temperature range from 5 to 125°C

Using a precise technique of scanning microcalorimetry the heat capacity differences between water and dilute aqueous solutions of ethanol, n-propanol, n-butanol and n-pentanol were measured from 5 to 125°C and the partial molar heat capacities of these substances in water were determined. It was found that the heat capacity increment for alcohol disolved in water is proportional to the number of the-CH ₂ ^– groups and decrease with a temperature increase. The heat capacity increment of hydration of non-polar groups is shown to be positive and large at room temperature and decreases in magnitude as the temperature increases. In contrast, the heat capacity increment of hydration of polar groups is negative at room tempreature and increases as the temperature increases. From the temperature dependence of the heat capacity increment one can assume that the water molecules solvated by the non-polar groups of the alcohols behave in a non-cooperative manner.     

Solubilities of rare earth lodates in aqueous and aqueous alcoholic solvent mixtures

The solubilities of thirteen iodates of rare earth metals in aqueous and aqueous alcoholic solvent mixtures at 25°C were measured. Methanol and ethanol were used as the alcoholic components, and the alcohol concentrations in solvent mixtures were between 0–40 mass percent. From the solubilities measured in this study and the published data, the recommended solubility values of eleven iodates of rare earth metals [Ln(IO₃)₃: Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb] in water at 25°C were decided by applying the guidelines of the IUPAC Solubility Data Project, and the solubilities of two iodates [Ln(IO₃)₃: Ce and Lu] are designated as tentative values. The change in solubility of lanthanide iodates in aqueous and aqueous alcoholic solvent mixtures as a function of lanthanide atomic number is discussed. The logarithm of the solubility decreases almost linearly with the reciprocal of the dielectric constant of the solvent mixture, as expected from Born's equation and its modifications.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Liquid-vapor equilibrium of dilute aqueous solutions of ethanol and 2-propanol

An automated vapor pressure apparatus has been used to obtain highly precise values of the total pressure and composition of aqueous solutions of ethanol and of 2-propanol in the water-rich region at 25 and 35°C. From these results, values of the partial pressures and fugacities of the components and osmotic coefficients have been inferred. Interaction virial coefficients derived from the present results are compared with interaction parameters previously reported for alcohol molecules in dilute aqueous solution. A discussion is given of the relative importance of hydrophobic effects and hydrogen-bonding in producing the unusual thermodynamic properties of aqueous alcohol solutions.     

Binding constants and partial molar volumes of primary alcohols in sodium dodecylsulfate micelles

The densities of methanol, ethanol, 1-propanol, 1-butanol and 1-hexanol were measured in aqueous solutions of sodium dodecylsulfate at 25°C. The partial molar volumes of the alcohols at infinite dilution in the aqueous surfactants solutions were calculated and discussed using a mass-action model for the alcohol distribution between the aqueous and the micellar phase. The partial molar volumes of the alcohols in the aqueous and in the micellar phases, and the ratios between the binding constant and the aggregation number, were calculated. The partial molar volume for all the alcohols in micellar phase is 10 cm³-mol^–1 smaller than that in octane. This can be related to the strong hydrophilic interaction between the head groups of the alcohol and the micellized surfactant. From the extrapolated values of the distribution constant and the partial molar volumes in the aqueous and micellar phases, the standard partial molar volume of heptanol in micellar solutions was found to decrease with increasing surfactant concentration. The standard free energy of transfer of alcohols from water to micelles was rationalized in terms of hydrophilic and hydrophobic contributions. A model is proposed in which the empty space around each solute is assumed to be the same in the gas and liquid phases, and is used to explain the behavior of micelles in the presence of amphiphilic solutes.     

Volumetric Properties of Nucleic Acid Bases and Nucleosides in Aqueous Ethanol, 1,2-Ethanediol, 2-Propanol, and 2-Methyl-2-Propanol at 25°C

Partial molar volumes of cytosine, uracil, thymine, cytidine, uridine, thymidine, and adenosine have been measured in different concentrations of aqueous ethanol, 1,2-ethanediol, 2-propanol, and 2-methyl-2-propanol at 25°C using densimetry. These data are utilized in conjunction with the partial molar volumes of these nucleic acid bases and nucleosides in water reported earlier to deduce the partial molar volumes of transfer from water to aqueous alcohol or diol. The results are explained in terms of likely solute–solvent interactions; the role of solvent in these interactions is discussed. The partial molar volume data are also used to calculate the contribution of –CH₂- groups in the nucleic acid base or solvent and of ribose in the nucleoside to the partial molar volume of transfer. The validity of group additivity in these systems is discussed.     

Solubility of Triethylamine in Calcium Chloride Aqueous Solutions from 20 to 35°C

Solubilities of triethylamine in aqueous calcium chloride solutions were measured at 20, 25, 30, and 35°C. The molalities in CaCl₂ of the aqueous solvents ranged from 0.01 to 0.1 mol-kg^–1. Data were evaluated from density measurements with a vibrating-tube densimeter. A least-squares method was used to fit experimental density data points, taken at 15°C, to a double polynomial equation. Triethylamine molalities of the saturated aqueous phases were estimated by interpolation from this equation. Solubilities and thermodynamic properties of transfer of Et₃N from water to salt solutions were interpreted in terms of hydrophobic and electrostatic perturbed domains in the hydration shells of the nonelectrolyte and of the cation of the salt, as a function of temperature and salt concentration.