The ``brineco2.hh`` fluidystems uses an incorrect gasDensity calculation in the private ``gasDensity_`` function. It returns the unchanged CO2 gas density, while the density function implies a lot more complex density calculation similar to the ``liquidDensity_``. This seems to be like this from the very first commit on git, but e.g. in a ``biofluidsystem.hh`` that was derived from the brineco2.hh a long time ago by @hommel on dumux-devel there is a more complex gasDensity calculation using Dalton's law available. (see below) I suggest we change/fix this once most tests pass, because this might change some results for the ``next`` branch. I am not sure, what we should do about the master (or 2.12). Additionally the normalization of some moleFractions etc. seems a little sketchy to me, but that might be necessary. Additionally the second the brineco2.hh still uses the deprecated xl and xg naming. This should be changed, while fixing this. ` static Scalar gasDensity_(Scalar T, Scalar pg, Scalar xgH2O) { Scalar pH2O = xgH2O*pg; //Dalton' Law Scalar pCO2 = pg - pH2O; Scalar gasDensityCO2 = CO2::gasDensity(T, pCO2); Scalar gasDensityH2O = H2O::gasDensity(T, pH2O); Scalar gasDensity = gasDensityCO2 + gasDensityH2O; return gasDensity; }`