Molar volumes of ions

Abstract

The data of the molar volumes of ions have been analyzed in order to draw conclusions on the structure of water in the vicinity of the ions. The ions are shown to fall into two distinct groups according to whether the parameter 2/Z/F at the dipole centre of the first water layer is smaller or larger than 0.5. The findings give strong support to Frank's suggestion of ice cluster formation in the structure promoting ions which are characterized by 2/Z/?>0*5. Some papers 1-5 have been concerned with the molar volumes of ions at infinite dilution. All explain the observed data in terms of an equation 4; = V"-V", where 4: is the ionic molar volume at infinite dilution, Ye the electrostriction volume loss, V" the intrinsic volume of the ion. It is generally accepted that V" is a function of the ionic radius, and Ye (at least for ions with a small electrostatic field) a function of 9 / r .Hepler 1 after assuming that 4; of C1-= 18.0 cm3 and that V" is proportional to r:, then fits the experimental data, by defining V" = 5-3 r: for cations and 4.6 r; for anions and Ve = 4.7 9 / r o for cations and 19 z2/r0 for anions, where ro is the crystal radius, thus using four arbitrary constants. Stokes and Robinson,2 dealing with monovalent anions only, started implicitly with the premises that Ye for the large anions, C1, Br, I is zero. They also assume that Y o is proportional to r: and then arrive at the conclusion that v" = 4.35 r:, which is the total space occupied by closely packed spheres of radius YO. The model leads to @ = 25.3 cms/mole

The P,V,T,x properties of binary aqueous chloride solutions up to T=573K and 100MPa

“…of parameters is 21, 21, 23, 23, 23, 8, and 7, respectively (table 3). The optimal m r and valid T, P, m range for the seven binary systems are also listed in [116] 17.00 [62] 16.80 [63] 26.89 [117] 17.06 [63] 16.63 [79] 26.81 [118] 17.10 [119] 16.65 [120] 26.85 [121] 16.85 [79] 16.61 [54] 26.91 [62] 16.60 [68] 16.64 [3] 26.98 [63] 16.99 [80] 16.62 [122] 26.87 [64] 16.96 [82] 16.62 [123] 26.84 [66] 16.91 [124] 16.61 [125] 26.85 [68] 16.99 [83] 16.62 [126] 17.03 [120] 16.62 [127] 17.13 [69] 16.61 [70] 16.81 [128] 16.71 [129] 18.20 [111] 16.72 [71] 16.73 [130] 16.68 [131] 16.87 [2] 16.68 [72] 16.45 [33] 16.62 [73] 17.59 [132] 16.58 [74] 16.20 [31] 16.68 …”

Evaluation of individual ionic partial molar volumes in aqueous solutions

“…(b) Glueckauf [20] (in 1944) obtained V ion ðH þ ; aq:Þ ¼ À4:26 cm 3 Á mol À1 , assuming that V hydr (salt) of the alkali metal (Na to Cs) chlorides is a linear function of 1/r effective and calculated V ion ðCl À Þ at 1/r effective = 0 (r effective = r ion + 5.5 nm, also for V intr ¼ V cryst ). (c) Mukerjee [14] (in 1961) obtained V ion ðH þ ; aq:Þ ¼ À4:5 cm 3 Á mol À1 , assuming that the V ion -values of the alkali metal and of the halide ions (except for Li + and F À ) become a smooth function of r 3 ion .…”

“…Among the ions of alkali halides, only the Li + proves to have high enough electrostatic field to keep a double layered hydrogen bonded primer hydration sphere [20,9]. With others, only the ''residence time" of the positively hydrated water molecules changes monotonously with their surface charge densities.…”

pVTx Properties of Hydrothermal Systems

“…Glueckauf (1965) postuled that the void space is a hollow sphere of radius r + a with a = 0.055 nm if one assumes that the void space of an ion with r = r H 2 O = 0.138 nm is equal to that for pure water. The electrostiction part of V i o is calculated from the Born equation (Born, 1920) for the standard partial molar Gibbs free energy of solvation, that is the work to bring an ion from vacuum and introduce it in the bulk of a solvent with dielectric constant e. Helgeson and co-workers Kirkham, 1974, 1976;Helgeson et al, 1981) developed an equation of state for aqueous electrolytes based on this continuum model.…”