Modeling of Salt Mixtures

Author: Michael Steiger, Andreas Nicolai

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Salt mixtures – terminology

Salt mixtures are solutions or solid material mixtures of salts. Of particular interest are the properties of dissolved mixtures, i.e. salt solutions. Therefore, in this article Salt mixture is understood to be a solution of one or more salts.

Different types of salt mixtures can be defined e.g. a solution of one cation and one anion is a binary solution, a solution of two cations and one anion or one cation and two anions forms a ternary solution, etc.

Definition of a salt mixture

A salt mixture is determined by the type and concentration of the ions it contains. A common concentration measurement for the definition of salt mixtures is molarity. It gives the amount of the dissolved ion in relation to the mass of the solute (water).

A binary 1 molar Na₂SO₄ solution consists of a mixture of m_Na = 2 mol/kg, m_SO₄ = 1 mol/kg. A ternary solution, produced from 1 mol NaCL and 3 mol NaNO₃ would result in the mixture m_Na = 4 mol/kg, m_Cl = 1 mol/kg, m_NO₃ = 1 mol/kg.

Properties of salt mixtures

The physical, chemical and thermodynamic properties of salt mixtures can, in part, be measured directly, in part be identified indirectly and otherwise only be estimated or predicted through the use of modeling.

List of properties

The following listed properties are functions of temperature and composition (type of ions and their concentration).

• Solution density
• Water activity
• Activity of ions
• Osmotic potential
• Thermal conductivity
• Specific thermal capacity
• Viscosity

an atom or molecule with a positive electrical charge

an atom or molecule with a negative electrical charge.