Department Surface Waters - Research and Management

ChemEQL - a software for the calculation of chemical equilibria

The program is a stand-alone version of ChemEQL, and different versions for Mac (.dmg) and Windows (.exe) are available. A Linux version can be provided on request. It calculates and draws thermodynamic equilibrium concentrations of species in complex chemical systems. It handles homogeneous solutions, dissolution, precipitation, titrations with acids, bases, or other components. Adsorption on up to five different particulate surfaces can be modeled with the choice of the Constant Capacitance, Diffuse Layer (Generalized Two Layer), Basic Stern Layer, or Triple Layer model to consider surface charges. Corrections for ionic strength can be made and activities calculated. Kinetic reactions can be simulated with one rate determining process in a system of otherwise fast thermodynamic chemical equilibrium. Two-dimensional logarithmic diagrams, such as pe-pH (Pourbaix), or generally pX vs. pY, can be calculated. A drawing option is implemented. A library with over 1700 thermodynamic stability constants allows quick access, comfortable creation of input matrices and hence easy use of the program. A second library contains more than 300 solubility products that can be introduced if solid phases are modeled. Both libraries can be altered and extended with new reactions and stability constants. Output data are formatted for .xls or for import in a graphic program.

ChemEQL is an extended and user-friendly version of the original program MICROQL by John Westall. It runs on MacOSX and Windows. The program is currently in use in both teaching and research.

A manual guides through the application in a practical way. Many representative examples are included demonstrating typical chemical problems. Download the manual and a folder with example files.


The program ChemEQL V3.2 is downloaded, installed on your computer and started by clicking into the respective ChemEQL icons on the right. The binary libraries CQLJ.SolidsLib and CQLJ.RegularLib are stored in application specific folders. Existing ChemEQL libraries on your computer from an older version of ChemEQL are not deleted or replaced but used by the new installation. The current version of Java (8u111) is included which is supported by MacOS Sierra and Windows 10. System requirements are given on the official Oracle site. The installation is a one-time process. As the program is not signed it can lead to an error message when the program is started. This requires an exception in your security settings.

This program is free for all. However, I ask you to reference this software in case of publication of data calculated with ChemEQL. 
ChemEQL is an open source code on Github. Please report bugs or feature-requests in the issue-tracker or by e-mail to: