Solution Chemistry

Densities (ρ), ultrasonic speeds (u), and excess molar volumes () of binary mixtures of some aromatic ketones in acrylonitrile have been measured over the entire range of composition at 308.15 K. From these experimental results, parameters such as the isentropic compressibilities K S , interaction parameter χ 12, Flory parameters, A i coefficients, standard deviations σ(Y E), and molar sound

The pK a constants and relative abundances of unionized and ionized forms of Montelukast sodium {the sodium salt of 2-[1-[[(1R)-1-[3-[2-(7-chloroquinolin-2-yl) ethenyl] phenyl]-3-[2-(2-hydroxypropan-2-yl)phenyl]propyl]sulfanylmethyl]cyclopropyl] acetic acid} and Levodropropizine {(2S)-3-(4-phenylpiperazin-1-yl)propane-1,2-diol} were determined potentiometrically from measurements at various pHs. These determinations were in order to relate their pK a values with their bioavailability and to provide chemical data to be used in their analysis.

CaCI2(oq) with 0242 5 d((nao!-kg-') 5 6.150 were measured with vibrating-t u b denrimetern beiwe~n 25 and 250°C a d llerar 70 and400 bars. Apparent molar volumes V+ cdculated firom the measured density differences were represenred with the Pilzer ionimmaction sreatmr, with uppropriare expressions chosen for the temperature and p r m w e dependence of the viriaI c o c f l c i e~s of the model. Ii wa.s f o r d ~h ! the partid molar volume at infinire dillrrion I$, m d the xecond and third viriQI coeficient.~ DV and CY, were n e c c s s q to represeni V+ ncm the e.riimoted experimertla! uncwlainly. The ionic-sfrengrh dependent p(')' term in the BV coemient war included in t h fit. The reprcsentdionfor V+ h a 7 bem integrated with respeci l o precsure ro esrablislir the pressure dependence of e r c~s free energies over the temperature range studied. The volumetric ~QIQ indicute rho! the logarithm of rhe man ionic acrivity coefficient, In y * ( C d J, imeasa by a mmchum of 0.3 ai 400 bars. 250°C. and 6 mol-LX-' a r compared wirh its vdw LZ saturation pressme. . CA 94720. 2~h a n i s u y Division, Oak Ridge Narional Laboratory, Oak Ridge, IW 37831 897 M m -~1 1 1 9 W 4 B m $ 0 7 5 O M o 1995 Plenum Publihmg Cmpomtiou bkss, S l r n m n , and Bodnsr

The development of a meaningful dissolution procedure for drug products with limited water solubility has been a challenge to both the pharmaceutical industry and the agencies that regulate them. On the other hand, poorly soluble drugs present a big problem in pharmaceutical formulations. Therefore, various methods to improve the dissolution of poorly soluble drugs have been reported and employing surfactants for this purpose is the leading approach. In spite of wide applications of Mefenamic acid, the enhancement of its solubility in water using surfactant systems has not been explored. Therefore, we have investigated the interaction between this drug and anionic (SDS, SDBS, DTAB, CTAB, TTAB) surfactants as well as non-ionic (Tween 20, Tween 40, Tween 60, Tween 80, Brij 30, Brij 35,Brij 56 and Brij 58) surfactants. The results show that, irrespective of the surfactant type, the solubility of Mefenamic acid increases with increase in concentration of a surfactant, leading to the conclusion that there is an association between the drug and the surfactants. The molar solubilization ratio, micelle-water partition coefficient (K M), binding constant (K) and the Gibbs energy of solubilization (DG o s) of the drug in the micelles were determined to yield a model to correlate the solubility with the structure of the surfactant used. An outcome of the results is that the order of solubility of this drug in non-ionic and ionic surfactants is Tween 80 [ Tween 60 [ Tween 40 [ Tween 20 and, in the case of the Brij series, is Brij56 [ Brij58 [ Brij35 [ Brij30, while in cationic and anionic surfactants the order is CTAB [ TTAB [ DTAB and SDBS [ SDS.

Dielectric relaxation studies of propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) have been carried out, for various mole fractions, at different temperatures using a LF impedance analyzer, Plunger method, and an Abbe’s refractometer in the radio, microwave and optical frequency regions, respectively. Kirkwood’s effective correlation factor, the corrective Kirkwood correlation factor, Bruggeman parameter, relaxation time, excess inverse relaxation

An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel-boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70°C. The calculated enthalpy and entropy at 25°C for the formation of the complex from boric acid and Ni 2? ions are respectively equal to (65.6 ± 3.1) kJÁmol-1 and (0.5 ± 11.1) JÁK-1 Ámol-1. The results of this study suggest that complexation of nickel ions by borates can significantly enhance the solubility of nickel metal and nickel oxide depending on the concentration of boric acid and pH. First principles calculations were investigated and tend to show that the complex is thermodynamically stable and the nickel cation in solution should interact more strongly with the B 3 O 3 OH ð Þ À 4 than with boric acid.

The structure of Bi(III) clusters in aqueous concentrated acidic perchlorate solutions has been studied by means of X-ray absorption spectroscopy (XAS). The XAS data show that the polynuclear [Bi 6 O 4 (OH) 4 ] 6? complex with a cage structure predominates at room temperature in acidic Bi-rich solutions. This complex breaks down to form mononuclear complexes with increasing temperature to 428 K. This behavior is consistent with theoretical predictions based on considerations of the electrostatic repulsion, which increases sharply as the dielectric constant of the solvent decreases with increasing temperature.

The solubilities of two nonsteroidal anti-inflammatory (MELOXICAM and CELECOXIB) drugs, were determined in aqueous solutions of nonionic (Tween 20, Tween 80, Brij 30, Brij 35, Triton X 100, Triton X 114) surfactants. These surfactants have different numbers of oxyethylene units and their micelles showed different aggregation numbers. It is shown that these surfactants have different abilities to solubilize NSAIDs drugs.

This work gives estimated values of the velocity correlation coefficients VCCs for ternary electrolyte solutions (the system may have a tracer ion as one of the components), utilizing available measured transport coefficients. The VCCs originate from linear response theory and give a deeper insight into the microdynamic structure of complex ionic solutions. By assuming Onsager's relation to be valid, ten sets of velocity correlation coefficients were calculated for a ternary system and were used to calculate the VCCs for 134 Cs + ion (present in trace amount) transport in aqueous solutions of CsCl and KCl at 25 • C. Keywords Velocity correlation coefficients • Cs + ion transport • Diffusion coefficients • Sliding cell method • Radioactive tracer technique • Aqueous CsCl solution • Aqueous KCl solution

In this work a surface tensiometric method was used to study the effect of the chain length of non-ionic surfactants, viz. ethoxylated sorbitan esters, on micellar composition, critical micellar concentration, mutual interaction parameter (β 12), and activity coefficients of the mixed micelles formed with the cationic surfactant cetylpyridinium chloride at 25 °C. The micellar characteristics evaluated using the Clint, Rubingh, and Blankschtein models deviated significantly from ideality, and were used to ascertain the validity of these theories. Thermodynamic stability in terms of Maeda’s approach and interfacial properties is also discussed.

The solubility of thallium(I) chloride has been measured in methanol + water mixtures (10, 20, 30, and 40%, w/w methanol) containing added sodium chloride at concentrations up to 1 mol-kg−1 at 25°C. The data were analyzed using Pitzer's equations, without making an explicit assumption of association of Tl+ and Cl− ions to ion pairs, by assuming that α is 3 instead of 2, the value used by Pitzer for strong electrolytes in aqueous solutions. It is found that reasonable fits of the experimental solubility data could be obtained without the need to introduce a formal association constant. This implies that the β(1) parameter plays the role of an association constant. β(0) and β(1) values are derived in addition to the mixture parameters, θTl,Na and ψTlNaCl. Application of the higher-order limiting-law correction for symmetrical mixing in the manner proposed by Pitzer led to perceptibly, although insignificantly, worse fits of the experimental data, so that this correction in its present form appears to be more of theoretical than practical interest.

Isothermal vapor-liquid equilibrium (VLE) data, at 25~ were determined by a saturation method for each of the six methanol or methyl acetate binary systems with dichloromethane, chloroform, and 1,2-trans-dichloroethylene. The experimental data satisfy the Redlich-Kister consistency test, and were correlated with five Gibbs free energy models. All the binary mixtures of methanol with the chlorinated compounds exhibit strong positive deviations from ideality while the mixtures of methyl acetate with the chlorinated compounds present negative deviations from ideal behavior.

We consider a lattice model for ternary solutions in which the lattice bonds are covered by molecules of types AA, BB, and AB, and the only interactions are between the molecular ends of a common lattice site. Using its equivalence with the standard Ising model for magnets, we derive the spinodal curve of the three-component model on the honeycomb lattice in the mean-field and Bethe-lattice approximations. The spinodal and the coexistence curves of the ternary solution are drawn at different values of the reduced temperature, the only parameter of the model. The particular case of a binary solution is also illustrated.

The development of a meaningful dissolution procedure for drug products with limited water solubility has been a challenge to both the pharmaceutical industry and the agencies that regulate them. On the other hand, poorly soluble drugs present a big problem in pharmaceutical formulations. Therefore, various methods to improve the dissolution of poorly soluble drugs have been reported and employing surfactants for this purpose is the leading approach. In spite of wide applications of Mefenamic acid, the enhancement of its solubility in water using surfactant systems has not been explored. Therefore, we have investigated the interaction between this drug and anionic (SDS, SDBS, DTAB, CTAB, TTAB) surfactants as well as non-ionic (Tween 20, Tween 40, Tween 60, Tween 80, Brij 30, Brij 35,Brij 56 and Brij 58) surfactants. The results show that, irrespective of the surfactant type, the solubility of Mefenamic acid increases with increase in concentration of a surfactant, leading to the conclusion that there is an association between the drug and the surfactants. The molar solubilization ratio, micelle-water partition coefficient (K M ), binding constant (K) and the Gibbs energy of solubilization (DG o s ) of the drug in the micelles were determined to yield a model to correlate the solubility with the structure of the surfactant used. An outcome of the results is that the order of solubility of this drug in non-ionic and ionic surfactants is Tween 80 [ Tween 60 [ Tween 40 [ Tween 20 and, in the case of the Brij series, is Brij56 [ Brij58 [ Brij35 [ Brij30, while in cationic and anionic surfactants the order is CTAB [ TTAB [ DTAB and SDBS [ SDS.

Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol, and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds of sound were combined with our previous densitity results to obtain the isentropic compressibility κ S . The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K S,m and its excess counterparts \(K_{S,m}^{\mathrm{E}}\) . The \(K_{S,m}^{\mathrm{E}}\) values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x i ln η i and excess Gibbs energies of activation for viscous flow ΔG ∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities \(\overline{K}_{\phi ,i}^{0}\) of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental results have also been discussed on the basis of IR measurements.

The apparent molal heat capacities +cp have been determined at 25~ ./'or phenol, meta-nitrophenol, para-nitrophenol, meta-eyanophenol, and paracyanophenol and the corresponding sodium salts in water at several concentrations. These values have been extrapolated to infinite dilution to provide the C.~ values from which the heat capacity changes for the ionization of the aqueous phenols have been calculated. The observed A-C~ values are virtually identical within experimental error for the phenols studied. The volume data needed to calculate the +-Cp values from the experimental data are also reported.

Apparent molar heat capacities $$C_{{\text{p}},\phi }$$ and volumes $$V_\phi$$ of aqueous trifluoromethanesulfonic (triflic) acid, HCF3SO3 (aq.) were determined with a Picker flow microcalorimeter and vibrating-tube densimeter at temperatures from 283 to 328 K and molalities from 0.05 to 9.5 mol-kg-1. Values of $$V_\phi$$ and $$C_{{\text{p}},\phi }$$ display a maximum near 0.8 mol-kg-1. $$V_\phi$$ also displays a shallow minimum at ~5

The study of physical properties of binary liquid mixtures is of great importance for understanding and characterization of intermolecular interactions. In the same way, some models attempt to correlate viscosity in liquid mixtures to release eventual interactions' structures and peculiar behaviors. Grunberg-Nissan parameters for viscosity () in isobutyric acid + water mixtures over the entire range of mole fractions under atmospheric pressure and from 302.15 K to 313.15 K were calculated from experimental dynamic viscosities presented in previous works. Many experimenters investigate physicochemical properties using numerous models to derive some interpretations and conclusions. The present work comes within the framework of correlating different used equations to restrict investigations with a minimum of number of these models. Relationship between the Grunberg-Nissan, Arrhenius and Jouyban-Acree parameters for viscosity in one critical binary mixture is shown.

Solvents have been parameterized by scales of dipolarity/polarizability π*, hydrogen-bond donor (HBD) strength α, and hydrogen-bond acceptor strength β. Linear dependence (LSER's) on these solvent parameters are used to correlate and predict a wide variety of solvent effects, as well as to provide an analysis in terms of knowledge and theoretical concepts of molecular structural effects. Some recent applications utilizing this approach are presented. Included are analyses of solvent effects on (a) the free energies of transfer of tetraalkylammonium halide ion pairs and dissociated ions, (b) rates of nucleophilic substitution reactions, (c) the contrast in solvent effects of water (HBD) and dimethyl sulfoxide (non-HBD) on the acidities of m- and p-substituted phenols, (d) partition coefficients of non-HBD solutes between solvent bilayers, and (e) family relationships between proton transfer (and non-protonic Lewis acid) basicities and corresponding β values for monomer HBA. A comprehensive summary of LSER with references is given.

Ethylhexyl triazone (EHT) is a sunscreen agent that is widely used in skin care product formulations, whose physicochemical properties have not been previously studied in detail. For this reason, solubility data were measured for EHT in ethanol (EtOH) + ethyl acetate (AcOEt) mixtures at five temperatures. By using the van't Hoff and Gibbs equations, the thermodynamic functions: Gibbs energy, enthalpy, and entropy of solution, and of mixing, were evaluated from these solubilities. The solubility is greatest in mixtures with 0.10 and 0.20 mass fraction EtOH, but decrease as the EtOH mass fraction increases in the solvent mixtures. By means of an enthalpy-entropy compensation analysis, a nonlinear H 0 soln versus G 0 soln compensation plot was obtained having both negative and positive slopes as the solvent composition was varied. Accordingly to these results, it follows that the driving function for solubility of EHT is the entropy for solutions rich in EtOH or AcOEt, whereas in mixtures of medium composition, the driving function is the enthalpy.

The three molal dissociation quotients for citric acid were measured potentiometrically with a hydrogen-electrode concentration cell from 5 to 150~ in NaCI solutions at ionic strengths of 0.1, 0.3, 0.6, and 1 molal. The molal dissociation quotients and available literature data at infinite dilution were fitted by empirical equations in the all-anionic form involving an extended Debye-HUckel term and up to five adjustable parameters involving functions of temperature and ionic strength. This treatment yielded the following thermodynamic quantities for the first dissociation equilibrium at 25~ log Kla = -3.127+0.002, AH~a = 4.1+0.2 kJ-mol -~, ASia = -46.3+0.7 J-K-Lmol -~, and ACPYa = -162-+ 7 J-K-Lmol-~; for the second acid dissociation equilibrium at 25~ log K2a = -4.759+0.001, AH~a = 2.2-+0.1, A~a =-83.8-+0.4, and ACP~a =-192-+ 15, and for the third dissociation equilibrium at 25~ log K3a = -6.397-+0.002, AH~a = -3.6-+0.2, A~a = -134.5+0.7, and ACp~a = -231+7.

ABSTRACT The solubility of ammonia in toluene has been measured at 398 K and at pressures up to 340 kPa using a static, synthetic and isochoric technique. The goal of the present study is to determine the equilibrium solubility of ammonia in toluene at a pressure and temperature regime that is relevant to the reaction conditions of amination of 1,3,5-trichloro-2,4,6-trinitrobenzene leading to the formation of 1,3,5-triamino-2,4,6-trinitro benzene. The ammonia solubility data in toluene were hitherto unavailable under these experimental conditions. The solubility data have also been compared with the result obtained from a direct sampling method. The results are in agreement with Krichevsky–Kasarnovsky equation. The Henry’s law constant at the reaction temperature has been determined.

Despite its success for modeling electrolyte thermodynamics in aqueous media, the use of the Pitzer approach for the investigation of electrolytes in nonaqueous or in mixed solvent media is still very limited. Further, a review of the literature reveals that there are no more than a few research groups who have used the exact form of the Pitzer-Simonson-Clegg (PSC) ion-interaction approach for the investigation of electrolytes in mixed solvent systems. As a continuation of our previous studies, the present investigation reports modeling of HCl in the 2-propanol + water mixed solvent system with the Pitzer, PSC and an extended form of the PSC ion-interaction approaches using the experimental potentiometric data from a cell containing pH glass membrane and Ag/AgCl electrodes. The electrochemical measurements were performed over the HCl molality range from 0.01 to 4.5 mol·kg −1 in mixed 2-propanol (x%) + water (100 − x%) solvents, with different solvent percent mass fractions (x% = 10, 20, 30, 40 and 50%) at 298.15 ± 0.05 K.

A Picker flow microcalorimeter and a flow densimeter were used to obtain apparent molar heat capacities and apparent molar volumes of aqueous solutions of Na3P04 and mixtures of Na,zHP04 and NaH2P04. Identical measurements were also made on solutions of tetramethylammonium salts to evaluate the importance of anion.cation interactions. The experimental apparent molar properties were analyzed in terms of a simple extended Debye-H~lckel model and the Pitzer ion-interaction model, both with a suitable treatment for the effect of chemical relaxation on heat capacities, to derive the partial molar properties of H2PO~(aq), HPO~(aq) and PO~(aq) at infinite dilution. The volume and heat capacity changes for the second and third ionization of H3PO4(aq) have been determined from the experimental data. The importance of ionic complexation with sodium is discussed.

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

Activity coefficient values for NaCl in ethanol-water mixtures containing 20, 40, 60, YO, 80 and 90 weight % ethanol are calculated from the emf for the galvanic cell Na-glass I NaCI (m), I120 (IO0-Y), EtOIl (I1), AgCI I Ag in which the weight % of the corresponding solvent is indicated in parentheses. The results obtained are analyzed by using different theoretical models. Chemical models which take into account the presence of ion pairs in solutions of high ethanol content are also used. There is good agreement between the results obtained from all the models.

The dielectric constants (relative permittivities) of water, methanol, ethanol, butanol and acetone were measured at 91.3 kPa and (283.15 and 293.15) K and are reported here. The dielectric constants were determined by using a new setup based on a low-pass filter. The obtained dielectric constant values are compared with those reported in the literature, and are consistent with those reported in the literature. The obtained dielectric constant data were also compared with those calculated by the Kirkwood model. The comparisons indicated that Kirkwood model can be successfully used for calculation of dielectric constants of the pure fluids.

This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag + and Pb 2+) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium, or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl} imide [EEIM][NTf 2 ], or [BEIM][NTf 2 ], or [HEIM][NTf 2 ], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF 6 ], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF 6 ] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF 6 ] for comparison. The effect of anion type (NTf − 2 versus PF − 6) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous solution into the ILs.

The determination of equilibrium constants is difficult when several chemical species are simultaneously present in solution. In this investigation, optical emission spectroscopic determinations of chromium(III) concentration in a 10 −4 mol·dm −3 solution, prepared from K 2 Cr 2 O 7 reduced in HNO 3 or HCl media, were used to construct the pCr (aq)

... Analysis Ameer Ghuzlaan · Mahmoud M. Al Omari · Khaldoun A. Al-Sou'od Received ... mass. Initially, the position of the CD macrocycle was fixed whereas the guest approached along the x-axis toward the wider rim of the CD cavity. The ...

The conductivity of LiOH aqueous solutions has been determined at 15, 25, and 45~ The data analysis showed that LiOH is a slightly associated electrolyte, its association increasing with temperature. The association constant and distance parameter obtained from the conductivity data were successfully employed to calculate the activity coefficients of the solutions. The same procedure applied to very precise conductivity data for NaOH aqueous solutions enabled us to assess the reliability of this method of calculation of activity coefficients up to 0.1 m. The alkali metal hydroxides show a reverse trend in the way their properties change with cationic radius, as is the case for the fluorides with which they are compared.

The solubilities of lanthanum carbonate La2(CO3)3·8H2O in solutionsS 0([H+]=H mol kg−1, [Na+]=(I−H) mol kg−1, [ClO 4 − ]=I mol kg−1) at various fixed partial pressures of CO2 have been investigated at 25.0 °C. The hydrogen ion molality and the total molality of La(III) ion in equilibrium with the solid phase were determined by e.m.f. and analytical methods, respectively. The stoichiometric solubility constants $$\log ^ \star K_{ps0}^I = \log \{ [La^{3 + } ]p_{CO_2 }^{3/2} [H^ + ]^{ - 3} \}$$ according to the overall reaction $$1/2La_2 (CO_3 )_3 \cdot 8H_2 O + 3H^ + \rightleftharpoons La^{3 + } + 3/2CO_2 + 11/2H_2 O$$ have the values 10.23, 10.37, 10.58, 10.77 and 11.06 forI=0.1, 0.25, 1.0, 2.0 and 4.0 mol kg−1 (Na)ClO4, respectively. The extrapolation to infinite dilution using the Pitzer equations resulted in a “thermodynamic” solubility constant: $$\log ^ \star K_{ps0}^0 = \log \{ ([La^{3 + } ]p_{CO_2 }^{3/2} [H^ + ]^{ - 3} )(\gamma _{La^3 } + \gamma _{H^ + }^{ - 3} )a_{H_2 O}^{11/2} \} = 9.57 \pm 0.05$$ . This in turn led to the Gibbs energy of lanthanite, La2(CO3)3·8H2O, formation: $$\Delta _f G_{298}^{O - } = - 5048.4 kJ mol^{ - 1}$$ . Die Löslichkeit von Lanthancarbonat La2(CO3)3·8H2O in LösungenS 0([H+]=H mol kg−1, [Na+]=(I−H) mol kg−1, [ClO 4 − ]=I mol kg−1) wurde bei 25.0 °C und verschiedenen, konstanten Partialdrücken von CO2 untersucht. Die Molalität der Wasserstoff- und die totale Molalität der La(III)-Ionen im Gleichgewicht mit der festen Phase wurden potentiometrisch bzw. analytisch bestimmt. Für die stöchiometrischen Löslichkeitskonstanten $$\log ^ \star K_{ps0}^I = \log \{ [La^{3 + } ]p_{CO_2 }^{3/2} [H^ + ]^{ - 3} \}$$ entsprechend der Gesamtreaktion $$1/2La_2 (CO_3 )_3 \cdot 8H_2 O + 3H^ + \rightleftharpoons La^{3 + } + 3/2CO_2 + 11/2H_2 O$$ wurden beiI=0.1, 0.25, 1.0, 2.0 und 4.0 mol kg−1 (Na)ClO4, folgende Werte gefunden: 10.23, 10.37, 10.58, 10.77 und 11.06. Die Extrapolation auf unendliche Verdünnung mit Hilfe der Pitzer-Gleichungen führte zu einer „thermodynamischen“ Löslichkeitskonstante von: $$\log ^ \star K_{ps0}^0 = \log \{ ([La^{3 + } ]p_{CO_2 }^{3/2} [H^ + ]^{ - 3} )(\gamma _{La^3 } + \gamma _{H^ + }^{ - 3} )a_{H_2 O}^{11/2} \} = 9.57 \pm 0.05$$ . Mit dieser ergab sich die freie Bildungsenthalpie von Lanthanit La2(CO3)3·8H2: zu: $$\Delta _f G_{298}^{O - } = - 5048.4 kJ mol^{ - 1}$$ .

The concentration dependent self-aggregation of 1,1 -diethyl-2,2 -carbocyanine chloride (pinacyanol chloride dye) in 7.5% (v/v) ethanol + 92.5% water solution in the range of 10 −6 -10 −3 mol·dm −3 has been investigated by quantitative UV/vis and derivative spectroscopy. Bands with maxima at 601, 546, 522, and 507 nm could be attributed, respectively, to the monomer, a sandwich-type dimer, a vibronic overtone of the dimer, and a higher aggregate, most probably a stacked trimeric form of the dye. Using the Peak-Fit program, the overlapping bands were separated and analyzed for all concentrations studied. From the spectral fitting routine, extinction coefficients of 192,000, 156,000, and 282,000 cm −1 ·mol −1 ·dm 3 were determined for the monomer, dimer and trimer respectively.

The surface tension and fluorescence measurements have been carried out to study the interactions
present between anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) and cationic surfactant,
dodecyltrimethylammonium bromide (DTAB), in aqueous solution, in presence and absence of additives
(glutamine, histidine and methionine) at different composition and temperature. Critical micelle concentrations
(CMCs) have been determined using surface tension measurement. In case of SDBS, the CMC
value increases with rise in temperature while in case of DTAB, it shows a U-type behavior, meaning
thereby, both hydrophobic and hydrophilic dehydration becomes prominent in case of DTAB while only
hydrophilic dehydration plays decisive role for the micellization to take place in case of SDBS. From
surface tension data, the surface excess concentration at air/water interface ( max), minimum area per
surfactant molecule (Amin) and the surface pressure at CMC (CMC) have been evaluated. Thermodynamic
parameters of transfer, adsorption and micellization have also been evaluated and discussed in detail.
Fluorescence probe study has been carried out to outline the results stated above. The CMC values calculated
using pyrene as a fluorescent probe at room temperature resembles well with the micellar values
determined using surface tension measurement.

Contrary to widely held beliefs, many concentrated aqueous solutions of strong electrolytes and nonelectrolytes are shown to behave ideally by calculating the activity of water (a w ) from vapor pressure data. The mole fraction of water (x w ) is equal to the water activity a w (Raoult's Law) when the mole fraction of water is calculated by accounting for water strongly bound to the solute, which is then not available to act as solvent. In this case

Densities of binary water + ethanol and ternary water + ethanol + LiNO 3 mixtures have been measured over the temperature range from 298 K to 448 K and at pressures up to 40 MPa using the constant-volume piezometer immersed in a precision liquid thermostat. The measurements for water + ethanol mixture were made for four compositions of 0.0163, 0.0343, 0.0730, and 0.0946 mol fraction of ethanol. The measurements for thernary water + ethanol + LiNO 3 mixtures were performed in the same temperature and pressure ranges for twelve concentrations. The combined expanded uncertainty of the density, pressure, temperature, and concentration measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.06%, 0.05%, 20 mK, and 0.015%, respectively. The derived volumetric properties such as excess (V E m ), apparent (V˚), and partial (V ∞ 2 ) molar volumes were calculated using the measured values of density for the binary water + ethanol mixture and for pure water and ethanol. The small and negative values of excess molar volume for the mixtures were found at all experimental temperatures, pressures, and over the entire concentration range. The excess molar volume minimum is found at concentration about 0.4 mol fraction of 1-propanol. The concentration minimum of the derived apparent molar volumes V˚near 2 mol kg −1 (dilute mixture) was observed.

Ultrasonic velocity measurements, density measurements and viscometric studies were conducted for the drug buspironehydrochloride (0.01–0.1 M) at three different concentrations (0.1, 0.05 and 0.025 M) at 298.15 K/1 atm. The buspirone hydrochlo-ride was prepared in aqueous solutions of Cu(II) and Co(II) metal ion. The experimental data were used to determine acousticalparameters, such as isentropic compressibility, intermolecular free length, specific acoustic impedance, relative association, freevolume, internal pressure, viscous relaxation time, Gibb’s free energy, attenuation coefficient, Rao’s constant, and Wada’s constant.The viscosity data were analysed using the Jones–Dole equation, and the values of the Falkenhagen coefficient A and Jones–DoleB-coefficient were calculated. The outcomes were expressed in terms of the molecular interactions and the variations in parametersunder varying solute concentrations. Concluding remarks regarding intermolecular interactions are provided.

The solubility of carefully characterized magnetite, Fe 3 04, m dilute aqueous solutions saturated with H 2 has been measured at temperatures from 100 to 300~ in a flow apparatus. Solution compositions included either HC1 or NaOH molalities of up to 1 and 40mmole-kg-1, respectively, and H 2 molalities of 0.0779, 0.779, and 8.57 mmole-kg-1. The dependence of the equilibrium solubE#y on the pH and reduction potential were fitted to a scheme of soluble ferrous and ferric species consisting of Fe 2+, FeOH

Densities, viscosities and speeds of sound of binary mixtures of ethanol, propan-1-ol, butan-1-ol and pentane-1-ol with n-butyl acetate have been measured over the entire range of composition at temperatures of 298.15, 303.15, 308.15 and 313.15 K and atmospheric pressure. From the experimental densities, viscosities and speeds of sound, the excess molar volumes V E, deviations in viscosity Δη, and deviations in isentropic compressibility Δκ S have been calculated. The excess molar volumes and deviations in isentropic compressibility are positive for all the binary systems studied over the whole composition, while deviations in viscosities are negative for all of the binary mixtures. The excess molar volumes, deviations in viscosity, and deviations in isentropic compressibility have been fitted to a Redlich–Kister type polynomial equation. FTIR and 1H-NMR studies of these mixtures are also reported.

Excess molar volumes, \(V_{123}^{\mathrm{E}}\) , of 1,3-dioxolane or 1,4-dioxane (1) + aniline (2) + benzene or toluene (3) ternary mixtures have been determined over the entire mole fraction range at 308.15 K. \(V_{123}^{\mathrm{E}}\) data have been fitted to the Redlich-Kister equation to evaluate ternary adjustable parameters and standard deviations. The observed \(V_{123}^{\mathrm{E}}\) data have been analyzed in terms of (i) Graph theory, (ii) Prigogine-Flory-Patterson theory, and (iii) Sanchez and Lacombe theory. It has been observed that \(V_{123}^{\mathrm{E}}\) values predicted by Graph theory compare well with the corresponding experimental values.