Hi Jan,
For properties like the vapor pressure we use the cosmo file as well as the gas phase energy in COSMOtherm.
If you like to combine the gas phase and the solution I would suggest to use the Gibbs free energy of solvation
from COSMOtherm and the gas phase Gibbs free energy from the TURBOMOLE gas phase caulations and freeh.
For the Gibbs free energy of reactions, for instance, we use gas phase DFT frequencies for the chemical
potential in the gas phase (freeh) together with DFT or maybe MP2 etc. gas phase energies. To get back to
the solution you need the Gibbs free energy of solution for all product and educts. You can get this values
from COSMOtherm. As input you need the cosmo files and gas phase energy files, which can be calculated
with TURBOMOLE. The Gibbs free energy of solvation can be calculated via the Henry constant option (Gsolv option).
Please be aware of the different definition of this value (the reference 1bar/1mol solvent should be OK for you).
hope thius helps,
michael