Solubility of inert gases in liquids as an example of spontaneously arising nanodispersions
L.N. Miserovsky, Doctor of science, Professor; P.R. Smirnov
G.A. Krestov Institute of Solution Chemistry of Russian Academy of Sciences
This report is devoted to thermodynamical analysis of inert gases – liquid system under isochore-isobaric conditions. The analysis is based on the following points:
1. According to [1] solubility of inert gases in liquids (mole to mole of liquid) is described by equation
| (1) |
here VLm is the molar volume of the liquid; k is the molecular packing coefficient of the liquid calculated by [2]; k* is the limiting value of this parameter corresponding to the condition n2 = 0; cg,∞ is the equilibrium gas concentration in the intrinsic phase, mol m–3; KD is the constant of gas particles partition between the intrinsic phase and its intermolecular volume (VL,f*), which is determined from the ratio
| (2) |
where VgW is the van der Waals volume of 1 mole of gas molecules.
2. Mole Gibbs energy of gas (Gg) at the temperature T and concentration equal to cg is subjected to equation
| Gg = Gg0 ± kh (cg – 1) + T ks ln cg, | (3) |
were Gg0 is standard (at the gas concentration 1 mol m-3) mole Gibbs energy at the temperature T; kh and ks are empirical constants.
3. Real transfer process of gas particles to volume of liquid is approximated by hypothetical process, that consists of two stages: transfer of some quantity of gas moles from own phase to physical micro volume numerically equal to VL,f*, and distribution of these gas particles into separate cavities of the gas.
Verification of the model is conducted on the example of noble gases and nitrogen solubility data in n-decane at 280 – 300 K.
As a result it has been determined that:
• biphasic bicomponent systems that arise at the contact of inert gases with liquids are thermodynamically unstable;
• the increase of Gibbs energy in these systems is connected with transition of liquid component to volume tense condition as a result of formation of the second gas component;
• the liquid, saturated by inert gas, can be considered a dispersion of gas clusters spontaneously formed in cavities of intermolecular volume;
• the energy required for the formation of the cavities for gas clusters is compensated externally by maintaining constant temperature.