The published uncertainty (1σ) in estimating ∆G * solv (H + ) is 1.7 kcal mol -1 for aqueous 81 and 2.4 kcal mol -1 for non-aqueous solvents. As discussed previously, the proton solvation free energy error is systematic for each solvent and not random. Combining these analyses, the overall uncertainties for ∆G * solv (A -) in D2A-dGsolv-anion are estimated to be 2.8 kcal mol -1 in water and 3.3 kcal mol -1 in non-aqueous solvents. These uncertainties were calculated through uncertainty propagation analysis, which involves combining the individual uncertainty contributions from the sources using the rootsum-of-squares method, assuming that the uncertainty contributions are independent. The overall uncertainties can be interpreted as 1σ confidence intervals, which have similar coverage probability to RMSE. To further assess the quality of data in D2A-dGsolv-anion, we compiled a small set of anionic solvation free energies composed only from experimental data. We obtained ∆G * solv (AH) values from dGsolvDB3/overlap 27 and ∆G o acid, gas (AH) values from NIST/overlap, 51 shifting the ∆G o acid, gas (AH) values by 1.2 kcal mol -1 to align with the QM calculations. We then used these data to compose a set of solvation free energies of anions (ExpSolv/overlap). We compared D2A-dGsolv-anion data to ExpSolv/overlap, comprised of 89 anions in water, 4 in DMF, 5 in methanol, and 7 in ethanol (Figure ). We use the same values of ∆G * solv (H + ) and pK a in both sets, so the remaining disagreement is from differences in ∆G o acid, gas (AH) and ∆G * solv (AH). Much of the deviation between D2A-dGsolv-anion and ExpSolv/overlap are from different values for gas-phase acidities. The MAE/RMSE between the QM-computed and experimental gas-phase acidities alone in this subset is 1.02/1.64 kcal mol -1 , which is consistent with the errors of 1.33 / 1.57 kcal mol -1 from comparing NIST/overlap with D2A-dGgas (see Figure ) as well as the higher uncertainty of the gas-phase calculations (Table ). We also repeated this analysis with the values in MNSol/overlap (see Figure ). We observe similar test statistics: an overall lower RMSE for water and higher RMSE in nonaqueous solvents methanol, DMSO, and acetonitrile. Unfortunately, the constituent values for ∆G * solv (A -) are not available in MNSol, and so we could not assess their disagreement with the D2A-dGsolv-anion values.