Abstract Fourier transform ion cyclotron resonance (FT-ICR) spectrometry was used to study and recheck the proton transfer equilibria for a large number of low-basicity compounds, particularly those which are less basic than H 2 O. The data obtained were used for the construction of a continuous scale of the relative gas-phase basicities between H 2 S and SO 2 F 2. The present results are compared with the results obtained by McMahon and co- ...