Aqueous Salt Solutions

Free demo program

Equilibrium calculations based on the Extended UNIQUAC model can be performed with Microsoft Excel® as user interface. A sample program can be downloaded for free. The program includes the ions Na+, H+, Cl-, HSO4-, SO42-, and OH-. Download the free demo program with Excel interface by clicking demo program for phase equilibrium salt calculations.

 The model can also be called by MATLAB from MathWorks®. In order to call the free demo program from MATLAB, you first need to download the program with Excel interface at the link above. In addition, you need a MATLAB header file which can be downloaded together with a small MATLAB script, and more information. Download header file and information about calling the model from MATLAB by clicking MATLAB_Information

Based on user input of temperature and composition, the program performs the following calculations:

The calculation accuracy achieved with this sample program is typical for the performance of the extended versions of the program too. The license will expire after approximately one year. After the license has expired, you can come back and download a new version. The sample program comes with a short  manual, that explains about installation and use of the program.

Extended versions of the program

Extended versions of the program containing additional ions and solvents can be generated according to the needs of customers. More advanced versions of the program with multi phase flash (vapor-liquid-solid and vapor-liquid-liquid-solid equilibrium calculations) can also be provided. Please tell us what ions you are interested in and we will send you a quote (

Integration with SysCAD Plant Simulation Software (

Our free demo program and extended versions of the program can be integrated with plant simulation software from SysCAD. SysCAD is a powerful and versatile plant simulation software, and can be used to simulate the simplest processing circuit through to a complex full plant operation. By integrating our software with SysCAD you can benefit the most from both software packages. Please contact SysCAD to purchase their software and the add-in required for the integration.

Pressure dependent solubility

An extended version of the program including the pressure dependency of solubility is available. This program contains the ions Na+, H+, Mg2+, Ca2+, Ba2+, Sr2+, Cl-, OH-, SO42-, HSO4-, CO32-, HCO3 and is meant for calculations of oil field scale or prediction of precipitation in geothermal energy production. More details about the oil field scaling calculation program here.

 Program calculations 

The program is called via the Microsoft Excel® file included in the download. In the excel file you can perform your own calculations with the model. You will also see a number of calculation examples which have been calculated already. These include:

A phase diagram for the binary NaCl - H2O system:

Phasediagram for the NaCl - H2O system

A phase diagram for the binary Na2SO4 - H2O system:

Phase diagram for the Na2SO4 - H2O system

A phase diagram for the binary NaOH - H2O system:

Phase diagram for the NaOH - H2O system

A triangular phase diagram for the ternary NaOH - Na2SO4 - H2O system at 30°C

Triangular phase diagram for the NaOH - Na2SO4 - H2O system at 30°C

A Phase diagram for the Na2SO4 - H2SO4 - H2O system at 82.5°C:

Phase diagram for the Na2SO4 - H2SO4 - H2O system

Osmotic coefficients for Na2SO4 in dilute and in supersaturated solutions at 25°C. The precipitation of glauber's salt, Na2SO4·10H2O starts at 1.9 molal Na2SO4:

Osmotic coefficients for Na2SO4 solutions in dilute to supersturated solutions

Mean molal activity coefficients of NaCl solutions at 50°C. The data plotted together with the calculated line are correlated data from Clarke E.C.W. and Glew, D.N., Evaluation of the thermodynamic functions for aqueous sodium chloride from equilibrium and calorimetric measurements below 154 C., J. Phys. Chem. Ref. Data, 14(1985)489-610 (2):

Mean molal activity coefficients of NaCl solutions