Correlations for the solubility of normal alkanoic acids ando-toluic acid in binary solvent mixtures

Reasonable estimates of ternary solid-liquid equilibrium can be obtained by application of the Wilson and UNIFAC models. The solubilities of octadecanoic, eicosanoic, docosanoic, and o-toluic acids in binary solvents consisting of a common component (cyclohexane) and a varying second component (heptane, ethanol, methanol, 2-propanol, and 1-butanol) have been measured by a dynamic method from 290 to 340 K. The systems containing cyclohexane-alcohols mixed solvents were found to exhibit a synergistic effect of solubility. The best prediction was obtained for the Wilson equation utilizing temperature dependent _ij parameters. For solubilities in nonpolar solvents, the standard deviations for predicted solubilities are comparable to the experimental errors.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Solubilities of the cyclodextrins in the presence of transition metal salts

The solubilities of -, -, and -cyclodextrin have been measured in the presence of the first row transition metals: Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺; chlorides, nitrates and sulphates (in this case Fe²⁺), and, for companson, with CaCl₂, the corresponding Group IIa salt. Where possible the measurements are reported as a function of the activity of the salts. In general, for the transition metals the sulphates all show a linear decrease in solubility with increasing salt activity: for the nitrates the solubility increases and then reaches a limiting value; and for the chlorides a small decrease in solubility is observed at low activity followed by an increase in solubility at higher salt activity. Circular dichroism measurements confirm that there is no direct complexation at non-basic pH.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August 1995.     

A spectroscopic investigation of the structure of alcohol-water solutions

The v₂ + v₃ combination band of water has been recorded for nine alcohol-water solutions in which the volume fraction of water is less than 2% and for three alcohol-water solutions over the entire range of composition. In dilute solutions it was found that the fraction of symmetrically bonded water was, in general, smaller than in aprotic solvent-water systems. The fraction of nonbonded water protons was greater in alcohols of higher molecular weight and was also greater in tertiary alcohols than in primary ones. The 2v_OH overtone band was recorded for three alcohols in alcohol-rich solutions. Water appears to break up the polymeric alcohol structure, and there appears to be a slight preference for water-water bonds over water-alcohol bonding. Raman spectra of the alcohol C–O stretching mode indicate that water-alcohol bonding is stronger than alcohol-alcohol bonding. The fraction of free alcohol and water OH groups appears to be smaller in solutions of intermediate composition than in the pure liquids. This increased structure of the solutions is consistent with the maxima occurring in the viscosity of alcohol-water solutions.     

Laser induced photoacoustic spectroscopy in liquid samples: temperature and solvent effects

Summary Laser induced photoacoustic spectroscopy (LIPAS) has been confirmed as an analytical tool, suitable for the determination of inorganic and organic species in aqueous and organic solvents, reaching detection limits two orders of magnitude lower than those obtained with conventional spectrophotometry.A significant influence of the solvent on the enhancement of the magnitude of the LIPAS response waveform of the piezoelectric detector has been found experimentally for inorganic species (neodymium ions) and organic compounds (e.g. -carotene and the cytochrome c), when water was replaced by organic solvents. This is particularly true, when a laser excitation wavelength above 500 nm was used, where the absorption coefficient for H₂O increases drastically.Furthermore, the temperature dependence of the magnitude of the LIPAS signal has been measured, in the range between 20–70°C in samples containing Nd³⁺,-carotene and the macromolecule cytochrome c in various aqueous and organic (polar and non-polar) solvents (H₂O, HClO₄, acetone, ethanol and petrol ether). A very strong enhancement of the LIPAS response was observed with increasing temperature (a factor of two in an interval between 20 and 40°C) for all inorganic and organic substances in aqueous solution. On the other hand, in polar and non-polar organic solvents only a slight decline of the signals of about 20% was found over the same temperature range.     

Studies on the Hydrolytic Behavior of Zirconium(IV)

The stability constants of zirconium(IV) hydrolysis species have been measured at 15, 25, and 35 °C [in 1.0 mol-dm^–3 (H,Na)ClO₄] using both potentiometry and solvent extraction. In addition, the solubility of [Zr(OH)₄(am)] has been investigated in a 1 mol-dm^–3 (Na,H)(ClO₄,OH) medium at 25 °C over a wide range of –log [H⁺] (0-15). The results indicate the presence of the monomeric species Zr(OH)³⁺, Zr(OH)₂ ²⁺, Zr(OH)₃ ⁺, and Zr(OH)₄ ⁰(aq) as well as the polymeric species Zr₄(OH)₈ ⁸⁺ and Zr₂(OH)₆ ²⁺. The solvent extraction measurements required the use of acetylacetone. As such, the stability constants of zirconium(IV) with acetylacetone were also measured using solvent extraction. All stability constants were found to be linear functions of the reciprocal of temperature (in kelvin) indicating that H ^o and S ^o are both independent of temperature (over the temperature range examined in the study). The results of the solubility experiments have shown four distinctly different solubility regions. In strongly acidic solutions, the solubility is controlled by the formation of polynuclear hydrolysis species in solution whereas in less acidic solution the formation of mononuclear hydrolysis species becomes dominant. The largest portion of the solubility curve is controlled by equilibrium with aqueous Zr(OH)₄ ⁰(aq) where the solubility is independent of the proton concentration. In alkaline solutions, the solubility increases due to formation of the zirconate ion. The middle region was used to determine the solubility constant (log *K _s10) of Zr(OH)₄(s). From the data in the alkaline region, a value of the stability of the zirconate ion has been determined. This is the first time that the possible evidence for the zirconate ion has been identified in aqueous solution that has previously been found only in the solid phase.     

Temperature Dependence of Chloride Complexation for the Trivalent f-Elements

The influence of elevated temperatures on the formation of 1:1 chloro complexes for Eu³⁺ and Am³⁺ are reported. Using a solvent extraction technique, stability constants for the equilibrium M_(aq) ³⁺+Cl_(aq) ^– MCl_(aq) ²⁺ have been measured in the temperature range of 25–75 °C. Modest increases in ₁ are observed, and small positive enthalpies for these reactions are reported. These data are discussed in the context of previous reports for the trivalent lanthanide and actinide chloro systems.     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

An attempt to parameterize the structuredness of solvents

An attempt has been made to parameterize the structuredness of solvents from the viewpoint of intermolecular interactions, and the structuredness parameter S _p has newly been proposed. The enthalpy of vaporization H _vap ^/o of various solvents has been considered to consist of donor-acceptor interaction energy (DA), which can been estimated from Gutmann's donor and acceptor numbers, some other interaction energies (VDW), which may not be fully described in terms of the donor-acceptor interactions and may be related to the electronic distribution, the volume and shape of the molecule, the polarizability and ionization potential of atoms in the molecule, the energies of these interactions being usually considered to be of Van der Waals type and possibly evaluated from the enthalpy of vaporization ofn-alkanes, and the intermolecular interaction energy (STR) due to the three-dimensional molecular ordering in the liquid: H _vap ^/o =DA+VDW+STR. The STR term obtained as the difference between H _vap ^/o and (DA+VDW) is defined as the structuredness parameter S _p , which is a dimensionless quantity by dividing the value with the (kJ-mol^–1) unit. The entropies of formation S ₁ ^o and S ₄ ^o of [MX]⁺ and [MX₄]^2– complexes, respectively, of divalent metal ions (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺) with halide and thiocyanate ions in aqueous and nonaqueous solvents could be represented as an almost linear function of the structuredness parameters S _p .     

Solubility and Solubility Product at 22°C of UO2(c) Precipitated from Aqueous U(IV) Solutions

Solubility studies on UO₂(c), precipitated at 90^°C from low-pH U(IV) solutions, were conducted under rigidly controlled redox conditions maintained by EuCl₂ as a function of pH and from the oversaturation direction. Samples were equilibrated for 24 days at 90^°C and then for 1 day at 22^°C. X-ray diffraction (XRD) analyses of the solid phases, along with the observed solubility behavior, identified UO₂(c) as the dominant phase at pH1.2 and UO₂(am) as the dominant phase at pH1.2. The UV-Vis-NIR spectra of the aqueous phases showed that aqueous uranium was present in the tetravalent state. Our ability to effectively maintain uranium in the tetravalent state during experiments and the recent availability of reliable values of Pitzer ion-interactionparameters for this system have helped to set reliable upper limits for the log K ^o value of –60.2 + 0.24 for the UO₂(c) solubility [UO₂(c) + 2H₂O U⁴⁺ + 4OH^–] and of >–11.6 for the formation of U(OH)₄(aq) [U⁴⁺+ 4H₂O U(OH)₄(aq) + 4H⁺]     

Temperature deactivation of excited Tb3+ in the presence of 1,2-dioxetane in acetonitrile

Quenching the fluorescence (FL) of terbium perchlorate by 2,2-adamantane-2,2-dioxide (1) was shown to have a chemical character and was caused by the formation of the [1...Tb³⁺] complex. The dependence of the lifetime () of FL of Tb^*3+ in acetonitrile on the temperature and concentration of1 has been studied. The temperature dependence of is caused by a rearrangement of the inner sphere of the aquasolvate complexes of Tb³⁺, which leads to the replacement of H₂O with MeCN and1. The energy of replacing the H₂O molecule in the inner sphere of complexes with a solvent molecule has been calculated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1762–1766, October, 1994.     

Relation between stability constants of metal ion cryptates in two solvents and the transfer activity coefficients of the metal ions

The extrathermodynamic assumption of Lejaille and Bessière that _1,2 log K (LM ⁿ⁺ )=–G _tr (M ⁿ⁺ ) in which K is stability constant and L is cryptand 2.2.2, 2 _B 2 _B 2, 2.2.1, or 2.1.1 has been tested in dipolar aprotic solvents for M ⁿ⁺ being Li⁺, Na⁺, K⁺, Ag⁺, Tl⁺, and Ba²⁺. The relation has been found generally acceptable for the dipolar aprotic solvents propylene carbonate, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide, provided the size of the ion is equal to or smaller than the cavity of the cryptand. The relation does not hold for the hydrogen bonded donating solvents, water, and methanol.     

Free energies of transfer of complexes of the type MCl2py4 between pyridine and other solvent media

Solubility isotherms are reported for the NiCl₂·4py, MnCl₂·4py, and MnCl₂·2py solid pyridinates in a number of pyridine+diluent mixtures at 25°C. Activity coefficients of the solvent components have been derived from the total vapor pressures measured by a static method. The standard free energies of transfer for the NiCl₂py₄ and MnCl₂py₄ complexes are the same, within the experimental error, in the pyridine+aprotic diluent mixtures, while marked differences are observed in the pyridine+chloroform mixtures. Marked deviations are observed for chloroform and 1,2-dichloroethane from a correlation between the standard free energy of transfer of the complexes, on one hand, and the Hildebrand's solubility parameter of the solvent, on the other, the latter correlation being roughly valid for aprotic solvents. The deviations are tentatively ascribed to hydrogen bond formation of the type H... between the protic solvents and the coordinated pyridine molecules, enhanced by the d electron delocalization.     

Dielectric relaxation studies of monoalcohol solutions with 1,2-diols

Dielectric relaxation processes in solutions of monoalcohols with ethanediol, 1,2-propanediol, and 1,2-butanediol have been studied using the dielectric time domain spectroscopy technique. The dielectric spectrum has been analyzed in terms of two dispersions. The influence of varying content of diol, and of chainlength of the alcohol, on the static dielectric constant _s and on the main dispersion is reported. For the long-chain alcohols _s is lowered and the main relaxation time successively shortened with the addition of diol to the solution. The results are compared to these found for aqueous alcohol solutions and discussed in terms of a structural model with rupturing of predominantly linear complexes on addition of water, diols, or on increasing the temperature.     

Nitration equilibrium in the glycerol-aqueous-nitric-acid system 3. PMR parameters,conformational structure,and main properties of glycerol and its nitrates

Studies of PMR spectra at a frequency of 294 MHz for glycerol, and its mono-, di-, and trinitrates have been carried out in aqueous solutions of nitric and sulfuric acids and in deuteroacetonitrile. The conformational composition weakly depends on the medium, temperature, and the number of nitrate groups in the molecule. Conformers with CH₂ and OH (or ONO₂) located in a trans position have a certain preference. The basicity parameters pK_BH+ and _e and semiprotonation points of glycerol (separately for primary and secondary hydroxyl) and glycerol dinitrates have been determined. In these properties glycerol and its dinitrates are similar to monatomic alcohols. Acidity functions of solutions of sulfuric and nitric acids were calculated using glycerol and glycerol dinitrates as indicators. Unlike Hammett bases, alcohols in H₂O-H₂SO₄ and H₂O-HNO₃ systems of identical molar composition are protonated practically identically.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 381–389, February, 1991.     

Ionic association in hydrogen-bonding solvents

Studies on ionic association in hydrogen-bonding solvents including water, aliphatic alcohols, fluorinated alcohols, formamide, ethylene glycol, and propanol-acetone mixtures are compared. Data were derived from measurements of conductivity, ultrasonic absorption, and viscosity of electrolyte solutions and diffusion of nonelectrolytes. It is concluded that electrolyte solvents can be divided into three categories according to whether they solvate effectively cations only, anions only, or both cations and anions. Water and most other hydrogenbonding solvents constitute the third class, a group in which patterns of ionic aggregation are very similar. Fluorinated alcohols belong to the second class, showing significantly different ion-pairing behavior.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.     

Compressibilities of cyclohexane and toluene mixtures at various temperatures

The isothermal compressibilities _T for cyclohexane+toluene mixtures at 25, 35, 45 and 60°C have been determined by direct piezometric measurement. By combining our results with supplementary literature data, we have calculated the isentropic compressibility _S. Values of the excess functions (V^E/_p)_T, _T ^E and _S ^E were also calculated at four temperatures and their behavior as a function of mole fraction and temperature was studied.     

Standard partial molar volumes of alcohols in aqueous dodecyltrimethylammonium bromide solutions

Density measurements of water-dodecyltrimethylammonium bromide (DTAB)-alcohol ternary systems as a function of alcohol and surfactant concentrations were carried out at 25°C. The alcohols were propanol (PrOH), 2-propanol (2-PrOH) and hexanol (HexOH). The apparent molar volume V_,R of alcohols have been calculated and the standard (infinite dilution) partial molar volumes of alcohols V _R at each surfactant concentration were obtained by means of a least squares fit of V_,R vs. the alcohol concentration. The V _R vs. surfactant concentration curves have been rationalized in terms of the partial molar volume of alcohol in the aqueous V _f and the micellar V _b phases and the distribution constant of alcohol between the aqueous and the micellar phases K. The V _b values for PrOH and HexOH together with those of butanol and pentanol previously reported satisfy the additivity rule giving a methylene group contribution of 16.7 cm³-mol^–1 which is identical to that reported in the literature from the study of pure liquid alcohols. No difference between V _b for PrOH and 2-PrOH has been found. From density data of water-alcohol and water-surfactant binary systems and of water-surfactant-alcohol ternary system, the apparent molar volume of the surfactant in the water-alcohol mixed solvent V_,S have been calculated as a function of the surfactant concentration and of the mixed solvent composition. The effect of the alkyl chain length of the alcohols and the effect of isomerization of the alcohols on the V_,S vs. surfactant concentration trends have been analyzed.     

Deficiencies of the ferricinium-ferrocene redox couple for estimating transfer energies of single ions

The difference between the partial molal entropies of ferrocene and ferricinium has been determined in nine solvents from the temperature dependence of the formal potential of the ferricinium-ferrocene redox couple using a nonisothermal electrochemical cell arrangement in order to probe possible structural reasons for the limitations of the ferrocene assumption for estimating the transfer thermodynamics of single ions between different solvents. In contrast to the uniformly small positive values of predicted by the Born model, the experimental quantities varied widely from small or even negative values in hydrogen-bonded solvents (–5 to 3 e.u.) to substantially larger values (11–14 e.u.) in dipolar aprotic media. These variations appear to arise chiefly from additional solvent ordering in the vicinity of the ferricinium cation compared to the ferrocene molecule which is enhanced in the aprotic solvents. The variations in between water and a number of nonaqueous solvents provide a predominate contribution to the differences between the free energies of single ion transfer calculated using the ferrocene and alternative extrathermodynamic assumptions.     

Partial molal volumes,expansibilities, and compressibilities for aqueous alcohol solutions between 5°C and 40°C

Density and ultrasound measurements have been carried out for aqueous solutions of primary and secondary alcohols and ,-diols at 5, 10, 20, and 40°C. The density data have been used to calculate partial molal volumes and expansibilities at infinite dilution. The ultrasound data have been used to calculate isentropic partial molal compressibilities which have been converted to isothermal values by using the expansibility data and literature data on partial molal heat capacities. The difference between the isentropic and isothermal partial molal compressibilities is practically zero at 5°C, and increases only slightly with temperature. Group partial molal compressibilities have been evaluated. The hydrophobic group compressibilities increase with temperature while the hydrophilic group compressibilities remain constant or decrease with temperature.