Equilibrium partial pressures of strong acids over concentrated saline solutions-I. HNO₃

Equilibrium partial pressures of HNO₃ have been measured at 25°C over concentrated aqueous solutions containing the ions H⁺, NO₃ ^-, SO₄ ^2-, K⁺, NH₄ ⁺ and Mg²⁺. Measurements agree closely with predictions made using a Henry's Law constant of 2.45 × 10⁶ mol² kg^-2 atm ^-1 for the reaction HNO_3(g) = H_(aq.) ⁺ + NO_3(aq.) ^-, and the Pitzer activity coefficient model. The model is recommended for the calculation of solute and solvent activities in aqueous aerosols at high ionic strength, corresponding to equilibrium relative humidities greater than about 70 %. The following new parameters have been estimated for the model using the partial pressure measurements and other thermodynamic data: ψ_{H,Na, NO}, -0.003; θ_{3 NO}, 0.0926; ψ₃,SO_{4 NO}, -0.0046; ψ₃,SO₄,K_NO, 0.0066; ψ₃,SO₄,Na_H,NH, -0.01; ψ₄,NO_{3 H,K,No}, -0.01. © 1988.₃₃