We currently have a ``simpleco2.hh`` for when CO2 is used as an ideal gas and a ``co2.hh``, which uses the values from the CO2Tables. We would like to have a CO2 component that chooses automatically between a "simple CO2" formulation (when used in the ideal gas regime) or the tabulated values from the CO2 tables (when used in the super-critical regime) or some interpolation between the two. * [ ] Define/Look up regime for ideal gas and super-critical state * [ ] Think of good and efficient interpolation * [ ] implement all **Discussion:** Should we include the option to "force" the use of either one, in case you really want to use CO2-Tables or the ideal gas law all the time?