Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

Abstract

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, μmol (kg-H₂O)⁻¹, have been fitted to a function of the molality m (standard deviation σ < 3μmol-kg⁻¹)

$$\ln \left( {\left[ {{\text{O}}_{\text{2}} } \right]^0 /\left[ {{\text{O}}_{\text{2}} } \right]} \right) = \ln \gamma \left( {{\text{O}}_2 } \right) = Am + Bm^2 $$

where A and B are adjustable parameters and the activity coefficient of oxygen γ)O₂) = [O₂]⁰/[O₂]. The limiting salting coefficient, k _S = (∂ln γ/∂ m)_m=0 = A, was determined for all salts. The salting coefficients for the chlorides and sodium salts showed a near linear correlation with the crystal molar volume V _cryst = 2.52 r ³. The salting coefficients determined from the Scaled Particle Theory were in reasonable agreement with the measured values. The activity coefficients of oxygen in the solutions have been interpreted using the Pitzer equation

$$\ln \gamma _{{\text{O}}_{\text{2}} } = 2\sum\limits_{\text{c}} {\lambda _{{\text{O}}_{\text{2}} {\text{c}}} m_{\text{c}} /m^{\text{0}} + 2\sum\limits_{\text{a}} {\lambda _{{\text{O}}_{\text{2}} {\text{a}}} m_{\text{a}} + } \sum\limits_{\text{c}} {\sum\limits_{\text{a}} {m_{\text{c}} m_{\text{a}} } } \zeta _{{\text{O}}_{\text{2}} {\text{ca}}} }$$

where $\lambda _{{\text{O}}_{\text{2}} {\text{i}}}$ is a parameter that accounts for the interaction of O₂ with cations (c) and anions (a) with molalities m _a and m _c, and $\zeta _{{\text{O}}_{\text{2}} {\text{ca}}}$ accounts for interactions for O₂ with the cation and anion pair (c-a). The $\lambda _{{\text{O}}_{\text{2}} {\text{i}}}$ and $\zeta _{{\text{O}}_{\text{2}} {\text{ca}}}$ coefficients determined for the most of the ions are in reasonable agreement with the tabulations of Clegg and Brimblecombe. The values of $\lambda _{{\text{O}}_{\text{2}} {\text{i}}}$ for most of the ions are a linear function of the electrostriction molar volume (Velect = V⁰ − V _cryst).