Osmotic coefficients and activity coefficients of aqueous hydrobromic acid solutions at 25°C

The osmotic coefficients ? and activity coefficients γ_± of aqueous solutions of HBr depend largely on emf measurements utilizing the silver-silver bromide electrode. There is evidence, however, that side reactions between AgBr and bromide ion render this electrode unreliable when the HBr molality (m) exceeds 2 mol-kg^?1. It is shown, however, that the isopiestic vapor-pressure technique is capable of yielding data for HBr at higher molalities. New emf measurements of cells with hydrogen and AgBr/Ag electrodes at 25°C have been combined with literature data to recommend values for the activity coefficients of HBr in the dilute range. These have been supplemented by isopiestic measurements vs. NaCl and CaCl₂ reference solutions in the range of HBr molalities from 0.7 to 6.2m. A table of ? and γ_± at 25°C at round molalities from 0.005 to 6.0 is presented.     

Osmotic and activity coefficients of perrhenic acid and perrhenate salts

Osmotic and activity coefficients are reported for the aqueous solution of perrhenic acid and for its lithium, sodium and tetramethylguanidinium slats at 25°C. These coefficients are similar in order of magnitude but smaller than the coefficients of the corresponding perchorates. Evidence is submitted for the ion pairing of the perrhenate ion with both hydronium and tetramethylguanidinium ions in fairly dilute aqueous solutions. The association with hydronium ion decreases in more concentrated solutions.     

Osmotic and activity coefficients of aqueous lithium sulfate solutions at 40°C

The osmotic coefficients for aqueous lithium sulfate solutions were experimentally determined at 40°C. Sodium chloride served as the isopiestic standard for the calculation of osmotic coefficients. The molality ranges covered in this study correspond to about 0.1–2.5 mol-kg^–1. The system of equations developed by Hamer-Wu and Pitzer were used to fit each set of osmotic coefficients. The parameters obtained from the fit were used to calculate the activity coefficients.     

Osmotic and activity coefficients of ammonium thiocyanate in aqueous solution at 25°C

Osmotic and activity coefficients of ammonium thiocyanate in aqueous solution at 25°C have been determined by the isopiestic vapor pressure method. The activity coefficients do not agree with values reported previously but are consistent with trends shown by activity coefficients of ammonium chloride and bromide.     

Osmotic and activity coefficients of ammonium thiocyanate in aqueous solutions at 25°C

Osmotic and activity coefficients of ammonium thiocyanate determined by the isopiestic vapor pressure method are compared with the data recently reported by Covington and Matheson. Activity coefficients calculated using the Pitzer equation are now in much better agreement although a systematic difference is evident in the two sets of data.Comment to the paper by Covingtonet al. (see ref. 2).We thank Mr. P. Kordes for programming.     

Osmotic and activity coefficients of sodium chloride-sorbitol and potassium chloride-sorbitol solutions at 25°C

Osmotic and activity coefficients are reported for sorbitol over the range 1.8–11.1m with NaCl as the reference and 1.8–7.6m with KCl as the reference electrolyte. The osmotic coefficients over the range 0–3.7m are identical with those reported earlier by Robinson. It was found that the activity coefficients of sorbitol are uniformly about four percent lower than those of dextrose. Activity coefficients of trace quantities of NaCl in concentrated sorbitol solutions are about one-half of their value in pure NaCl solutions while the activity coefficients of trace quantities of sorbitol in concentrated NaCl solutions are about one-third of their value in pure sorbitol solutions. Potassium chloride lowers the activity coefficient of sorbitol less than does sodium chloride in solutions of similar water activity. Sorbitol lowers the activity coefficients of potassium chloride in concentrated solution but actually elevates them in dilute solutions.     

Osmotic and activity coefficients at 25°C for tetraalkylammonium bromides in deuterium oxide

Earlier work by Lindenbaum and Boyd has demonstrated the important role of hydrophobic interactions involving the water solvent in determining the osmotic coefficients and properties of aqueous solutions of the tetraalkylammonium halides. Osmotic coefficients of solutions of tetramethyl-, tetraethyl-, tetrapropyl-, and tetrabutylammonium bromides in the more highly structured solvent D₂O have now been determined by the gravimetric isopiestic method, using reference solutions of NaCl in D₂O. The data were fitted to the Rush-Johnson and Pitzer equations. Satisfactory agreement with the results for aqueous solutions at comparable concentrations indicates that the solution chemistry of these quaternary ammonium bromides is not highly dependent on the degree of structure of the pure solvents. Supplementary data for mixtures of Me₄NBr with Et₄NBr, Pr₄NBr, or Bu₄NBr in both H₂O and D₂O are consistent with this conclusion.On leave 1980–82 from Banaras Hindu University, India     

Osmotic and activity coefficients of aqueous NaTcO4 and NaReO4 solutions at 25°C

Isopiestic vapor-pressure comparison experiments were performed with aqueous binary sodium perchlorate, pertechnetate, and perrhenate solutions to concentrations of approximately 8.5 m. Osmotic coefficients for these solutions and mean molal ionic activity coefficients for NaTcO₄ and NaReO₄ were derived from the isotonic molalities. Pitzer's treatment was applied to describe the concentration dependence of the osmotic coefficients of NaClO₄, NaTcO₄, and NaReO₄, and the implications of the parameters derived from a leastsquares fit are discussed in terms of solvent structure and interionic forces.     

Osmotic and activity coefficients of monomethyl-, dimethyl-, and trimethylammonium chlorides at 25°C

The osmotic and activity coefficients of monomethyl-, dimethyl-, and trimethylammonium chlorides in aqueous solution have been determined at 25°C by the gravimetric isopiestic method. The measurements extend from 0.1 molal (m) to 20, 17, and 15 mol-kg^–1, respectively, for the three salts. In the region below 2m, the osmotic coefficients decrease in the order NH₄Cl>MeH₃NCl>Me₂H₂NCl>Me₃HNCl>Me₄NCl, and above 3m the order is reversed. The intermediate members of the series have identical osmotic coefficients at the crossover molality of 3.0. It is suggested that the behavior at low molalities reflects primarily ion-dipole interactions, decreasing as the cation size increases, whereas hydrophobic (structure-making) interactions, increasing in importance with the number of non-polar methyl substituents, are predominant in concentrated solutions of these salts.     

Osmotic and activity coefficients of aqueous bile salt solutions at 25, 37, and 45°C

Osmotic coefficients measured by vapor pressure osmometry are reported for aqueous bile salt solutions at 25, 37, and 45°C. Solute activities decrease rapidly with increasing concentration due to premicellar association and micelle formation. In all cases, activities of the dihydroxy bile salts are lower than those of the trihydroxy bile salts. Osmotic coefficients and activity coefficients increase with increasing temperature. It is suggested that hydrophobic forces contribute substantially to the stability of primary bile salt aggregates and micelles.     

Osmotic and activity coefficients in the ternary system water — calcium chloride—urea at 298.15 K

Solvent activities and molal osmotic coefficients have been determined in the ternary system water—calcium chloride—urea at 298.15 K by means of an isopiestic method. Thermodynamic expressions are used to calculate molal activity coefficients of the solutes as well as Gibbs free energies of transfer from binary to ternary solutions.In the title system, the strong interactions of the dissolved components are indicated by the high, negative G^E values and the non-linear course of the isolines of solvent activity.     

Osmotic coefficients of electrolyte solutions

In this paper, the osmotic coefficient, phi, of electrolyte solutions is considered. According to the Gibbs-Duhem equation, the calculation of phi follows from that of the mean activity coefficient, gamma, based on a pseudolattice approach recently proposed. For any given electrolyte, the whole range of concentrations providing gamma相似文献   

Osmotic coefficients of aqueous sodium carbonate solutions at 25°C

Isopiestic vapor pressure measurements are reported for aqueous sodium carbonate solutions at 25°C using sodium chloride as reference electrolyte. Osmotic and activity coefficients are calculated from the concentrations of the solutions in isopiestic equilibrium. The results are used to calculate the trace activity coefficients of carbonate ion in sodium chloride solutions; these should approximate the trace activity coefficient of carbonate ion in seawater. The solubility of sodium carbonate in water at 25°C has been determined.     

Dilute sulfuric acid pretreatment of corn stover at high solids concentrations

Applied Biochemistry and Biotechnology - The enzymatic digestibility of a pretreated substrate is enhanced by increasing the severity of the pretreatment conditions, apparently because a greater...     

Osmotic and activity coefficients in dilute solutions of ethanol in cyclohexane from freezing-point measurements

The calorimeter developed in this laboratory for isothermal enthalpy-of-dilution measurements is adapted for use as an adiabatic calorimeter for freezing-point studies. Results are obtained for ethanol solutions in cyclohexane at mole fractions of ethanol from 0.001 up to 0.08. Activities calculated from the results are used to test association models.     

Osmotic and activity coefficients of the sodium salts of formic,acetic and propionic acids

Osmotic and activity coefficients are reported for the sodium salts of formic, acetic and propionic acids to the limits of their solubilities. Hydration of the second kind appears to increase with the length of the hydrocarbon chains. The onset of micelle formation is indicated in the more concentrated sodium propionate solutions.     

Osmotic coefficients of aqueous rare-earth perchlorates and nitrates

Osmotic coefficients of aqueous solutions of La(ClO₄)₃, Pr(ClO₄)₃, Nd(ClO₄)₃, Sm(ClO₄)₃, Gd(ClO₄)₃, Dy(ClO₄)₃, Ho(ClO₄)₃, Er(ClO₄)₃, Tm(ClO₄)₃, Yb(ClO₄)₃, Lu(ClO₄)₃, Nd(NO₃)₃, Sm(NO₃)₃, and Gd(NO₃)₃ in the molality range from 0.1 mol kg^?1 nearly to saturation at 298.15 K have been determined by the isopiestic method. The results obtained agree very well with those of Rard et al. published recently. A distinct two-series effect has been observed for the constant-molality values of rare-earth perchlorates. The results are discussed in terms of hydration of the cations and ionic association.     

Development of xylose-fermenting yeasts for ethanol production at high acetic acid concentrations

Mutants resistant to comparatively high levels of acetic acid were isolated from the xylose-fermenting yeastsCandida shehatae andPichia stipitis by adapting these cultures to increasing concentrations of acetic acid grown in shake-flask cultures. These mutants were tested for their ability to ferment xylose in presence of high acetic acid concentrations, in acid hydrolysates of wood, and in hardwood spent sulfite liquor, and compared with their wild-type counterparts and between themselves. TheP. stipitis mutant exhibited faster fermentation times, better tolerance to acid hydrolysates, and tolerance to lower pH.     

Osmotic and activity coefficients of two macrocyclic aminals in aqueous solution at 288.15, 293.15, 298.15 and 303.15 K

The osmotic coefficients of 1,3,5,7-tetrazatricyclo (3.3.1.13,7) decane (HMT) and 1,3,6,8-tetrazatricyclo (4.4.1.13,8) dodecane (TATD) in aqueous solutions were measured at 288.15, 293.15, 298.15 and 303.15 K. The technique used was the isopiestic. The data were used to calculate the activity coefficients of the two solutes at the four temperatures. The few data points found for HMT in literature at 298.15 K agree well with the new data. The reinforcement of water structure by the two aminals is discussed.