Conductivity of Sodium Chloride in Water + 1,4-Dioxane Mixtures at Temperatures from 5 to 35°C I. Dilute Solutions

The molar and single-ion conductivities of dilute solutions of sodium chloride (C<0.01 mol-dm^–3) in binary mixtures of 1,4-dioxane with water were measured covering a broad solvent composition range at temperatures from 5 to 35°C. Accurate viscosity and permittivity data were determined for the organic solvent system. Evaluation of the limiting molar conductivity , ionic conductivities. ₊ , and _– , and the association constant K _A is based on the chemical model of electrolyte solutions, including short-range forces.     

Determination of Stoichiometric Dissociation Constants of Benzoic Acid in Aqueous Sodium or Potassium Chloride Solutions at 25°C

Equations were determined for the calculation of the stoichiometric (molality scale) dissociation constant K_m of benzoic acid in dilute aqueous NaCl and KCl solutions at 25°C from the thermodynamic dissociation constant K_a of this acid and from the ionic strength I_m of the solution. The salt alone determines mostly the ionic strength of the solutions considered in this study and the equations for K_m were based on the single-ion activity coefficient equations of the Hückel type. The existing literature data obtained by conductance measurements and by electromotive force (EMF) measurements on Harned cells were first used to revise the thermodynamic value of the dissociation constant of benzoic acid. A value of K_a = (6.326 ± 0.005) × 10^-5 was obtained from the most precise conductivity set [Brockman and Kilpatrick] and this value is supported within their precisions by the less precise conductivity set of Dippy and Williams and by the EMF data set measured by Jones and Parton with quinhydrone electrodes. The new data measured by potentiometric titrations in a glass electrode cell were then used for the estimation of the parameters of the Hückel equations of benzoate ions. The resulting parameters were also tested with the existing literature data measured by cells with and without a liquid junction. The Hückel parameters suggested here are close to those determined previously for anions resulting from aromatic and aliphatic carboxylic acids. By means of the calculation method based on the Hückel equations, K_m can be obtained almost within experimental error at least up to I_m of about 0.5 mol-kg_-1 for benzoic acid in NaCl and KCl solutions.     

Re-evaluation of Activity Coefficients in Dilute Aqueous Hydrobromic and Hydriodic Acid Solutions at Temperatures from 0 to 60 °C

Simple two-parameter Hückel equations can be used for the calculation of the activity coefficients in aqueous hydrobromic and hydriodic acid solutions at temperatures from 0 to 60 °C and from 0 to 50 °C, respectively, at least up to a molality of 0.5 mol·kg^?1. The data measured by Macaskill and Bates (J. Solution Chem. 12:607–619, 1983) at 25 °C and those measured by Hetzer et al. (J. Phys. Chem. 68:1929–1933, 1964) at various temperatures on galvanic cells without a liquid junction were used in the parameter estimations for the hydrogen bromide (HBr) and hydrogen iodide (HI) solutions, respectively. The latter data consist of sets from 0 to 50 °C at intervals of 5 °C. The parameter values for HBr solutions were also tested using the numerous galvanic cell points from the other three data sets existing in the literature for hydrobromic acid solutions and covering wide range of temperatures from 0 to 60 °C. It was observed in the parameter estimations and tests that all of the estimated parameters are independent of the temperature. The recommended parameter values were additionally tested using the isopiestic data of Macaskill and Bates (see the citation above) and those of Harned and Robinson (Trans. Faraday Soc. 37:302–307, 1941) for dilute HBr and HI solutions at 25 °C, respectively. In more concentrated solutions up to a HBr molality of 4.5 mol·kg^?1 and up to a HI molality of 3.0 mol·kg^?1, an extended Hückel equation was used, which contains an additional quadratic term with respect to the molality. The parameters for the extended Hückel equations were determined from these isopiestic data and tested using these data and the existing galvanic cell data. The activity and osmotic coefficients calculated from the resulting equations are recommended in the present study for the more concentrated solutions. The recommended values are compared to the activity values reported in several previous tabulations.     

Viscosity of Aqueous Solutions of Lithium,Sodium, Potassium,Rubidium and Caesium Cyclohexylsulfamates from 293.15 to 323.15 K

The viscosities of aqueous solutions of lithium, sodium, potassium, rubidium and caesium cyclohexylsulfamates were measured at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity data were analyzed and interpreted in terms of the Kaminsky equation, η _r=1+Ac ^1/2+Bc+Dc ². The viscosity A-coefficient was calculated from the Falkenhagen-Dole theory. The viscosity B-coefficients are positive and relatively large. Their temperature coefficient ∂ B/∂ T is negative or near zero for lithium and sodium salts whereas for potassium, rubidium and caesium salts it is positive. The viscosity D-coefficient is positive. This was explained by the size of the ions, structural solute–solute interactions, hydrodynamic effect, and by higher terms of the long-range Debye-Hückel type of forces. From the viscosity B-coefficients the thermodynamic functions of activation of viscous flow were calculated. The limiting partial molar Gibbs energy of activation of viscous flow of the solute was divided into contributions due to solvent molecules and the solute in the transition state. The activation energy of the solvent molecules was calculated using the limiting Gibbs energy of activation for the conductance of the solute ions. The activation energy of the solvent molecules was then discussed in terms of the nature of the alkali-metal ions and their influence on the structure of water. The limiting activation entropy and enthalpy of the solute for activation of viscous flow were interpreted by ion-solvent bond formation or breaking in the transition state of the solvent. The hydration numbers of the investigated electrolytes were calculated from the specific viscosity of the solutions.     

Conductivity of Sodium Chloride in Water + 1,4-Dioxane Mixtures from 5 to 35°C II. Concentrated Solution

Conductivity data of sodium chloride in binary mixtures of water and 1,4-dioxanefrom 5 to 35°C were measured, covering an electrolyte concentration range upto the limit of solubility in the solvent mixtures and up to 5 mol-dm^–3 inpure water. Data analysis is based on the mean spherical approximation (MSA).Comparison is made with the data representation by the empirical Casteel-Amisequation. The association constants of the MSA are compared with those fromchemical model calculations at low concentrations (lcCM).     

Determination of the Glass Electrode Parameters by Means of Potentiometric Titration of Acetic Acid in Aqueous Sodium or Potassium Chloride Solutions at 25°C

Single-ion activity coefficient equations are presented for the calculation of stoichiometric (molality scale) dissociation constants K _m for acetic acid in aqueous NaCl or KCl solutions at 25°C. These equations are of the Pitzer or Hückel type and apply to the case where the inert electrolyte alone determines the ionic strength of the acetic acid solution considered. K _m for a certain ionic strength can be calculated from the thermodynamic dissociation constant K _a by means of the equations for ionic activity coefficients. The data used in the estimation of the parameters for the activity coefficient equations were taken from the literature. In these data were included results of measurements on galvanic cells without a liquid junction (i.e., on cells of the Harned type). Despite the theoretical difficulties associated with the single-ion activity coefficients, K _m can be calculated for acetic acid in NaCl or KCl solutions by the Pitzer or Hückel method (the two methods give practically identical K _m values) almost within experimental error at least up to ionic strengths of about 1 mol-kg^–1. Potentiometric acetic acid titrations with base solutions (NaOH or KOH) were performed in a glass electrode cell at constant ionic strengths adjusted by NaCl or KCl. These titrations were analyzed by equation E = E _o + k(RT/F) ln[m(H⁺)], where m(H⁺) is the molality of protons, and E is the electromotive force measured. m(H⁺) was calculated for each titration point from the volume of the base solution added by using the stoichiometric dissociation constant K _m obtained by the Pitzer or Hückel method. During each base titration at a constant ionic strength, E _o and k in this equation were observed to be constants and were determined by linear regression analysis. The use of this equation in the analysis of potentiometric glass electrode data represents an improvement when compared to the common methods in use for two reasons. No activity coefficients are needed and problems associated with liquid junction potentials have been eliminated.     

Raman-Spectroscopic Measurements of the First Dissociation Constant of Aqueous Phosphoric Acid Solution from 5 to 301 °C

Dilute aqueous phosphoric acid solutions have been studied by Raman spectroscopy at room temperature and over a broad temperature range from 5 to 301?°C. R-normalized spectra (Bose?CEinstein correction) have been constructed and used for quantitative analysis. The vibrational modes of H₃PO₄(aq) (pseudo C_3v symmetry) have been assigned. The band with the highest intensity, the symmetric stretch ?? _s{P(OH)₃}(?? ₁(a ₁)) is strongly polarized while ?? ₄(e), the antisymmetric stretch ?? _asP(OH)₃) is depolarized. The stretching mode of the phosphoryl group (?CP=O), ?? ₂(a₁) occurs at 1178?cm^?1 and is polarized. In the range between 300 and 600?cm^?1, the deformation modes are observed. The deformation mode, ??{PO?CH}, involving the O?CH group has been detected at 1250?cm^?1 as a very weak and broad mode. In addition to the modes of phosphoric acid, modes of the dissociation product $\mathrm{H}_{2}\mathrm{PO}_{4}^{ -}(\mathrm{aq})$ have been observed. The mode at 1077?cm^?1 has been assigned to ?? _s{PO₂}, and the mode at 877?cm^?1 to ?? _s{P(OH)₂} which is overlapped by ?? _s{P(OH)₃} of H₃PO₄(aq). The modes of $\mathrm{H}_{2}\mathrm{PO}_{4}^{ -} \mathrm{(aq)}$ have been measured in dilute solution and were assigned and presented as well. H₃PO₄ is hydrated in aqueous solution, which can be verified with Raman spectroscopy by following the modes ?? ₂(a₁) and ?? ₁(a₁) as a function of temperature. These modes show a strong temperature dependency. The mode ?? ₁(a₁) broadens and shifts to lower wavenumbers. The mode ?? ₂(a₁) on the other hand, shifts to higher wavenumbers and broadens considerably with increases in temperature. At 301?°C the phosphoric acid is almost molecular in nature. In very dilute H₃PO₄ solutions at room temperature, however, the dissociation product, $\mathrm{H}_{2}\mathrm{PO}_{4}^{ -} \mathrm{(aq)}$ is the dominant species. In these dilute H₃PO₄(aq) solutions no spectroscopic features could be detected for a hydrogen bonded dimeric species of the formula $\mathrm{H}_{5}\mathrm{P}_{2}\mathrm{O}_{8}^{ -}$ (or the neutral dimeric acid H₆P₂O₈). Pyrophosphate formation, although favored at high temperatures, could not be detected in dilute solution even at 301?°C due to the high water activity. In highly concentrated solutions, however, pyrophosphate formation is observable and in hydrate melts the formation of pyrophosphate is already noticeable at room temperature. Quantitative Raman measurements have been carried out to follow the dissociation of H₃PO₄(aq) over a very broad temperature range. In the temperature interval from 5.0 to 301.0?°C the pK ₁ values for H₃PO₄(aq) have been determined and thermodynamic data have been derived.     

Conductance of Lithium and Sodium Perchlorates and Tetraphenylborates in 2-Butanone from −35 to 25°C

Conductances of dilute solutions of LiClO₄, NaClO₄, LiBPh₄ and NaBPh₄ in 2-butanone were measured at seven temperatures from ?35 to 25°C. The limiting molar conductivities and association constants were evaluated using the conductance equation of Fuoss and Justice (including the Chen effect). The distance parameter was fixed at the Bjerrum distance. The limiting ionic conductivities, determined by assuming equal ionic conductivities of the i-Am₃ BuN⁺ and BPh ₄ ^? ions at all temperatures, were related to the crystallographic ionic radii using the Hubbard–Onsager model of dielectric friction corrected for the inhomogeneity of the electric field. The activation enthalpy of ionic transport in 2-butanone is almost independent of the nature of the electrolyte. The Walden products do not vary with the temperature. The correction to the conductance parameters for dielectric saturation computed for M⁺ClO ₄ ^? associates was found to be small. Thermodynamic functions characterizing the association process were evaluated from K _A data and their dependences on the temperature. The short-range, noncoulombic contributions to the Gibbs energy were estimated using Bjerrum's theory.     

Cadmium Malonate Complexation in Aqueous Sodium Trifluoromethanesulfonate Media to 75°C; Including Dissociation Quotients of Malonic Acid

The molal formation quotients for cadmium–malonate complexes were measured potentiometrically from 5 to 75°C, at ionic strengths of 0.1, 0.3, 0.6 and 1.0 molal in aqueous sodium trifluoromethanesulfonate (NaTr) media. In addition, the stepwise dissociation quotients for malonic acid were measured in the same medium from 5 to 100°C, at ionic strengths of 0.1, 0.3, 0.6, and 1.0 molal by the same method. The dissociation quotients for malonic acid were modeled as a function of temperature and ionic strength with empirical equations formulated such that the equilibrium constants at infinite dilution were consistent, within the error estimates, with the malonic acid dissociation constants obtained in NaCl media. The equilibrium constants calculated for the dissociation of malonic acid at 25°C and infinite dilution are log K _1a=-2.86 ± 0.01 and log K _2a=-5.71 ± 0.01. A single Cd–malonate species, CdCH₂C₂O₄, was identified from the complexation study and the formation quotients for this species were also modeled as a function of temperature and ionic strength. Thermodynamic parameters obtained by differentiating the equation with respect to temperature for the formation of CdCH₂C₂O₄ at 25°C and infinite dilution are: K = 3.45 ± 0.09, S° = 7 ± 6 kJ-mol^-1, S° = 91 ± 22 J-K^--mol^-1, and C _p ^o =400±300 J­K^-1­mol^-1.     

Conductance of Dilute Hydrochloric Acid Solutions to 458 K and 1.4 MPa

Electrical conductance measurements were made on dilute solutions of hydrochloric acid to 458 K and 1.4 MPa with a flow instrument. These measurements agree well with those of previous authors. The conductance theory of Fuoss and Hsia as given by Fernandez-Prini (FHFP), was fit to these measurements. It was found that this theory adequately described the present results with a single parameter, the limiting conductance at infinite dilution Λ°(HCl). Within their estimated accuracy, reported literature results of Λ°(HCl) between 264.15 and 579 K and high pressures were found to be represented by a five-parameter equation that was a function of the solvent viscosity, temperature and pressure. This equation along with the FHFP theory permits accurate calculation of the conductance of dilute hydrochloric acid solutions at high temperatures and pressures. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Partial Molar Volumes of Transfer of Some Amino Acids from Water to Aqueous Glycerol Solutions at 25°C

Apparent molar volumes of glycine, DL--alanine, L-valine, L-leucine, and L-phenylalanine in 0.5, 1.0, 2.0, 3.5, and 5.0 m _B (mol-kg^–1) aqueous solutions of glycerol have been obtained from solution densities at 25°C using precise vibrating-tube digital densimeter. The estimated partial molar volumes at infinite dilution V ^o ₂ have been used to obtain the corresponding transfer volumes _tr V ₂ ^o from water to different glycerol–water mixtures. The transfer volumes are positive for glycine and DL--alanine, and both positive and negative for the other amino acids over the concentration range studied. Interaction coefficients have been obtained from McMillan–Mayer approach and the data have been interpreted in terms of solute–cosolute interactions.     

Effect of Ammonium Salts on the Volumetric and Viscometric Behavior of D(+)-Glucose,D(−)-Fructose and Sucrose in Aqueous Solutions at 25°C

Apparent molar volumes, V _φ, and viscosity, η, of D(+)-glucose, D(−)-fructose and sucrose in water and in 0.02, 0.05, 0.5, 1.0 and 2.0 mol·kg⁻¹ aqueous solutions of ammonium bromide, tetraethylammonium bromide and tetra-n-butylammonium bromide have been determined at 25 °C from density and efflux time measurements by using a vibrating-tube digital densimeter and a capillary viscometer, respectively. Partial molar volumes, , at infinite dilution that were extrapolated from the V _φ data were used to obtain the corresponding transfer volumes, , for saccharides from water to different aqueous solutions of co-solutes. The Jones-Dole equation viscosity B-coefficients were obtained from the viscosity data. Positive values of were obtained for the saccharides in the presence of ammonium bromide, whereas both positive and negative values were obtained in the presence of tetraethylammonium and tetra-n-butylammonium bromides. The negative values at very low concentrations have small magnitudes. Volumetric interaction coefficients have been calculated by using the McMillan-Mayer theory and Gibbs energies of activation of viscous flow have been calculated by using Feakin’s transition-state theory equation. The parameters obtained from the volumetric and viscometric studies were used to understand various mixing effects due to the interactions between saccharides and ammonium salts in aqueous solutions.     

The Heats of Mixing of Aqueous Solutions of Dipeptides with Solutions of Nitric Acid and Potassium Hydroxide over the Temperature Range 288.15–308.15 K

The heats of interaction of D,L-α-alanyl-D,L-valine, β-alanyl-β-alanine, and α-alanyl-β-alanine with solutions of nitric acid and potassium hydroxide were determined calorimetrically at 288.15, 298.15, and 308.15 K and solution ion strengths of 0.5, 1.0, and 1.5 in the presence of KNO₃ and LiNO₃. The heat effects of step dissociation of the dipeptides were calculated using the RRSU universal program. The standard thermodynamic characteristics (Δ_r H ^o, Δ_r G ^o, Δ_r S ^o, and ΔC _p ^o) of proton interaction with the ligands specified were determined. The data obtained were analyzed in terms of Herny concepts. The thermodynamic characteristics of ionization correlated with the structural features of the dipeptides.     

Sorption–Desorption Photometric Determination of Trace Iron in Sodium, Potassium, and Ammonium Thiocyanates Using Polyurethane Foams

A reagent-free sorption photometric method for determining trace iron(III) in alkali-metal and ammonium thiocyanates was developed. The method consists in the adsorption of iron(III) thiocyanate complexes on polyurethane foams at pH 2–3 followed by the desorption of complexes with acetone and a measurement of the absorbance of solutions. The analytical range for iron was 0.5–20 g in a 0.2–2.5-g portion of salt. The determination limit and relative standard deviation were 2 × 10^–5% and 20–30%, respectively (n= 3; P= 0.95). The specific feature of the determination is that an additional photometric reagent is not introduced in the solution of the salt to be analyzed, because thiocyanate, that is, the matrix component of the test sample, acts as such a reagent.     

Application of β-Zeolite,Zeolite Y,and Mordenite as Adsorbents to Remove Mercury from Aqueous Solutions

In the present study, adsorption capacity of mercury(II) on β-zeolite, zeolite Y, and mordenite is investigated. It has been observed that removal rate of Hg(II) is better with zeolite Y than β-zeolite and mordenite, whereas, adsorption capacity of β-zeolite is found to be more than that of zeolite Y and mordenite. Five equilibrium isotherms have been tested to fit the adsorption data. The kinetic data are analyzed using the pseudo-first order, pseudo-second order, and diffusion models. The Freundlich isotherm model shows better fit for β-zeolite and zeolite Y, whereas, in the case of mordenite, Temkin isotherm fits the data well. The kinetic data of adsorption of Hg(II) on β-zeolite, zeolite Y, and mordenite fit well with pseudo-second order. Diffusion studies show that the adsorption of mercury on β-zeolite and zeolite Y are intraparticle diffusion controlled, and mordenite is film-diffusion controlled.     

Volumetric Properties of Some α-Amino Acids in Aqueous Guanidine Hydrochloride at 5, 15, 25, and 35°C

The infinite-dilution apparent molar volumesV ₂ ^o for glycine, DL-alanine, DL--amino-n-butyric acid, DL-valine, DL-leucine, and L-serine in 6 mol-kg^–1 aqueous guanidine hydrochloride were determined at 5, 15, 25, and 35°C from precise density measurements. Using these data, the standard volumes of transfer, _t V°, from water to 6m> aqueous guanidine hydrochloride solution were calculated. A linear relationship was found between V ₂ ^o and temperature. Both V ₂ ^o and _t V° vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. The results show that the apparent molar volumes at infinite dilution for (NH ₃ ⁺ ,COO^-) groups increase with increasing temperature and those for CH₂ and the other alkyl chains are almost constant. These results also shows that guanidine hydrochloride has stronger interactions with amino acids than urea. These phenomena are discussed in terms of the cosphere overlap model.     

Thermodynamics of protonation of AMP,ADP, and ATP from 50 to 125°C

The interaction of adenosine 5-monophosphate (AMP), adenosine 5-diphosphate (ADP), and adenosine 5-triphosphate (ATP) ions with protons in aqueous solution has been studied calorimetrically from 50 to 125°C and 1.52 MPa. At each temperature, the reaction of acidic AMP with tetramethylammonium hydroxide was combined with the heat of ionization for water to obtain the enthalpy of protonation of AMP, while the reactions of HCl with deprotonated tetramethylammonium salts of ADP and ATP were used to obtain the enthalpies of protonation of ADP and ATP. Equilibrium constant K, enthalpy change H^o, entropy change S^o, and heat capacity change C _p ^o values were calculated for the stepwise protonation reactions as a function of temperature. The reactions involving the first protonation of AMP, ADP, and ATP and the third protonation of ADP and ATP were endothermic over the temperature range studied, while that involving the second protonation is exothermic for AMP and ADP, but is exothermic below 100°C and endothermic at 125°C in the case of ATP. Consequently, log K values for the first and third protonation reactions (phosphate groups) increase while those for the second protonation reaction (N₁-adenine) decrease in the cases of AMP and ADP and go through a minimum in the case of ATP as temperature increases. The H^o values for all protonation reactions increase with temperature. The magnitude and the trend for the H^o, S^o, and C _p ^o values with temperature are discussed in terms of solvent-solute interactions. The magnitude of the C _p ^o values for the second protonation is consistent with little interaction between the phosphate ion and the protonated N₁ site of the adenine moiety in AMP, but indicates moderate interaction between these groups in ADP, and strong interaction in ATP.     

Reactive Extraction of Citric Acid Using Tri-n-octylamine in Nontoxic Natural Diluents: Part 1—Equilibrium Studies from Aqueous Solutions

Use of cheap, nontoxic, and selective solvents could economically provide a solution to the recovery of carboxylic acids produced by the bioroute. In this regard in the present paper, reactive extraction of citric acid was studied. Problems encompassing the recovery of the acid ([H₃A] _aq ^o ?=?0.1?C0.8) was solved by using tertiary amine (tri-n-octylamine, TOA) in natural diluents (rice bran oil, sunflower oil, soybean oil, and sesame oil). TOA was very effective in removal of acid providing distribution coefficient (D) as high as 18.51 (E%?=?95?%), 12.82 (E%?=?93?%), 15.09 (E%?=?94?%), and 16.28 (E%?=?94?%) when used with rice bran oil, sunflower oil, soybean oil, and sesame oil, respectively. Overall extraction constants and association numbers for TOA + rice bran oil, TOA + sunflower oil, TOA + soybean oil, and TOA + sesame oil were evaluated to be 35.48 (mol/l)^?1.46, 29.79 (mol/l)^?1.30, 33.79 (mol/l)^?1.51, and 37.64 (mol/l)^?1.65 and 1.46, 1.30, 1.51, and 1.65, respectively. Specific equilibrium complexation constants (K _E(n/m)) were also predicted using mathematical modeling.