Concerning experimental equilibria determined from P ssNMR, only the first equilibrium (H3PO4 H2PO4 -; pKa1) is consistent with this trend as it is lowered to pH 1.7. In opposition, the second (H2PO4 - HPO4 2-; pKa2) and the third (HPO4 2-PO4 3-; pKa3) equilibria are found lower than expected at pH 6.7 and 11.4, respectively. However, equilibria determination at -120 0 C must be taken with caution, as P spinning side band manifold decomposition is particularly sensitive and can induce important variations in the determined phosphate proportions (±10%). The use of higher static magnetic fields would help in this determination as the CSA contribution in the NMR spectra increases with the magnetic field. Moreover, we have to keep in mind that in our samples, phosphates are not dispersed in liquid solutions but in vitrified solids and that chemical equilibria may be strongly influenced. In any case, it is certain that the final temperature alone does not control the equilibria in the cryofixed solutions, since at -120°C it would induce the following pKa: pKa1 = 2.89, pKa2 = 11.18 and pKa3 = 18.55.