A thermodynamic model for calculating nitrogen solubility, gas phase composition and density of the N2–H2O–NaCl system

A thermodynamic model is presented to calculate N2 solubility in pure water (273–590 K and 1–600 bar) and aqueous NaCl solutions (273–400 K, 1–600 bar and 0–6 mol kg−1) with or close to experimental accuracy. This model is based on a semi-empirical equation used to calculate gas phase composition of the H2O–N2 system and a specific particle interaction theory for liquid phase. With the parameters evaluated from N2–H2O–NaCl system and using a simple approach, the model is extended to predict the N2 solubility in seawater accurately. Liquid phase density of N2–H2O–NaCl system at phase equilibrium and the homogenization pressure of fluid inclusions containing N2–H2O–NaCl can be calculated from this model. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.