Ionic Interactions in Aqueous Mixtures of NaCl with Guanidinium Chloride:  Osmotic Coefficients, Densities, Speeds of Sound, Surface Tensions, Viscosities, and the Derived Properties

Abstract

The isopiestic osmotic coefficients, densities, and speeds of sound of aqueous mixtures of NaCl with guanidinium chloride (GnCl) have been measured at different ionic strengths with varying compositions at 298.15 K with a view to determine the ionic interactions. The excess free energy, Δm G E, volume, Δm V E, and compressibility of mixing, Δm K E, of the NaCl−GnCl mixtures at constant ionic strength show interesting features with changing ionic strength fractions of the electrolytes. These excess properties of mixing with both negative and positive signs can be attributed to the mixing of hydrophilic and hydrophobic ions. It is shown that the binary and ternary interaction terms play an important role in the accurate representation of the osmotic coefficients, activity coefficients, volumes, and compressibilities of the mixtures. Measurements on the surface tension and viscosity of the NaCl−GnCl mixtures have also been reported. A simple equation incorporating like charge interactions has been employed to correlate the surface tension of the mixtures. The mixture viscosities have also been estimated from the parameters of pure NaCl and GnCl with an empirical mixing rule.

Cation Effect on the Water Activity of Ternary (S)-Aminobutanedioic Acid Magnesium Salt Solutions at 298.15 and 310.15 K

“…Further, osmotic coefficients of some other aminomethanamidine halides in aqueous binary mixtures are presented in the literature at 298.15 K, and also some for aqueous solutions containing other salts, e.g., GndmNO 3 , GndmClO 4 , GndmBz, and GndmPr . Activity of water in ternary aqueous mixtures with Gndm + salts at 298.15 K was investigated by Kumar − for mixtures cotaining GndmCl + NaCl, GndmCl + KCl, GndmCl + MgCl 2 , GndmCl + (C 4 H 9 ) 4 NCl, GndmNO 3 + NaCl, and GndmClO 4 + NaCl. Ternary mixtures of GndmCl with amino acids (glycine, l -leucine) and peptides (diglycine, triglycine, glycyl- l -leucine, l -leucyl- l -leucine) were investigated by Vesnaver et al Vapor-pressure osmometry was used to derive ratios of activity coefficients.…”

From Water Clustering to Osmotic Coefficients

“…For many electrolyte solutions, the osmotic coefficient (and van’t Hoff factor) is a strong function of electrolyte concentration. The osmotic coefficient as a function of concentration of electrolyte in some cases shows a distinct minimum as illustrated in Figure . − The figure contains osmotic coefficients obtained from a selection of literature studies. It is by no means a comprehensive review of all available literature, but an illustration of the concentration dependence of the osmotic coefficient.…”

“…Osmotic coefficients as a function of electrolyte molality from literature for (a) NaCl, − (b) NH 4 Cl, ,,, (c) Na 2 SO 4 , ,,− and (d) (NH 4 ) 2 SO 4 . − ,− …”

“…The osmotic coefficient as a function of concentration of electrolyte in some cases shows a distinct minimum as illustrated in Figure 1. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] The figure contains osmotic coefficients obtained from a selection of literature studies. It is by no means a comprehensive review of all available literature, but an illustration of the concentration dependence of the osmotic coefficient.…”

Densities of aqueous solutions containing model compounds of amino acids and ionic salts at T=298.15K

“…The important tools to investigate the interactions between ionic salts and amino acids are volumetric properties [14][15][16][17][18][19] and thermodynamic properties [20][21][22], such as free energy, entropy and enthalpy of amino acids in aqueous electrolyte solutions. These results lead to the conclusion that some of electrolytes can stabilize biological important molecules such as proteins.…”