Osmotic coefficients of aqueous solutions of seven compounds at 0.deg.

Abstract

Aqueous sulfuric acid and urea have been used as isopiestic standards to derive the 0°C osmotic coefficients for NaCI, KCI, CaCI2, Na2S04, and MgS04.

Vapor pressures and isopiestic molalities of concentrated CaCl2(aq), CaBr2(aq), and NaCl(aq) to T=523 K

“…Other low-temperature data sources included freezing-point data measurements of Gibbard and Fong [55] for freezing-point depressions reaching 4 K (0.0275 mol AE kg À1 to 0.73 mol AE kg À1 CaCl 2 ) and of Oakes et al [56] for freezing-point depressions reaching 50 K (4.0 mol AE kg À1 CaCl 2 ), and the isopiestic results using sulfuric acid as the reference standard at T = 288.15 K of Childs and Platford [57] and at T = 273.15 K of Platford [58] at molalities from (0.5 to 7) mol AE kg À1 . While the accuracy of the model decreases significantly with temperature decreasing below 298.15 K, since the freezing point data for very low temperature are much less accurate due to the approximations necessary for calculation of the osmotic coefficients, and no results are available for dilute solutions, a qualitatively reasonable behavior of the model was achieved at temperatures significantly below 273 K.…”

The activity and osmotic coefficients of aqueous calcium chloride at 298.15 K

“…~, defined by ACTIVITY COEFFICIENTS OF CALCIUM CHLORIDE 387 (16) where mi is the molality of the ith ion. For a single electrolyte tmi=vm and (17) or (18) The osmotic coefficient, ~, and the solute mean activity coefficient, y, are related through eqs (18), (15), (11), and 7, to give din y=(~-I)dm/m rd~, (19) which can be integrated to give…”

“…OsmQtic cQefficients fQr the data Qf RQbinsQn [15] are presented in table 1 and, thQse Qf Stokes [16], appear in tables 2 and 3. (43) PlatfQrd [18] has used H 2 S0 4 as an iSQpiestic standard fQr several salts at 0 °c. He used the ~ fQr H 2 S0 4 at 25°C and enthalpy data to' Qbtain the QsmQtic cQefficient at 0 °c and then used the H2S04 as a reference to' obtain ~ fQr CaCb at 0 °c, SO' there is nO' advantage in reversing the calculatiQns to' redetermine ~ at 25°C fQr CaCb frQm the 0 °c data.…”

“…The values of the activity coefficients are reported at rounded molalities over a range of 0.001 to 1 , mol, kg-I. These data are presented in table 18 but have not been used in the evaluation due to the availability of original freezing point data. These data agree well with the activity coefficients calculated from eq [39], and are apparently based on the results of Loomis [53].…”

Evaluated activity and osmotic coefficients for aqueous solutions: thirty-six uni-bivalent electrolytes

“…Emf measurements on the cell Na(Hg)l<(1); Na2S04(m); H9 2 S0 h (s), Hg(1 The data for Na2S04 are remarkably consistent and appear to be, for the most part, hiqhly reI iable. There are several distinct isopiestic investigations [20,24,33,35,47,49,50,51] involving the use of four different reference electrolytes (unfortunately neither Platford [33] nor Frolov and Nasanova [20] reported their mea.sured isopiestic molal ities) that are, with the exception of a few scattered measurements, in excellent agreement with each other and with the more carefully done of the direct vapor pressure measurements [22, 23,37]. The.…”