For reference we use the MNSOL data set, which contains experimental solvation free energies of neutral and singly-charged molecules with atom-types of H, C, N, O, F, Si, P, S, Cl, Br, and I. Here we focus mainly only the aqueous solvation subset of that data set. Because iodine is not supported by 6-31G(d) we removed compounds test2018, test4001-4 and test4007-9 from the reference data set. Compounds c091 and i091 are radicals and are not included because PM6 is only implemented for RHF in GAMESS. Our final reference set of molecules then consists of 522 aqueous solvation free energies of which 81 are for anions and 60 are for cations and we refer to this as the MNSOL data set.