This project has been funded by the German Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV, grant agreement No. 0325217), the European Union's Horizon 2020 Research and Innovation Programme (grant agreement No. 850626) and the Helmholtz Association. In the context of the German national geoscientific large-scale infrastructure project GeoLaB (https://www.geolab.kit.edu/english/index.php).

This data publication presents newly acquired viscosity data for synthetic aqueous solutions of sodium chloride (NaCl) and calcium chloride (CaCl₂), which have been prepared in a single salt and mixed form. The solutions covered a wide range of concentrations and mixing ratios representative of those encountered in geothermal settings. The data presented here span temperatures between 293 K and 353 K at ambient pressure.

The measured data were obtained at the Laboratory for Fluid physics at GFZ German Research Centre for Geosciences.