For comparison, CO3 2-/HCO3 -equilibria in carbonate vitrified solutions determined by C DNP MAS at 100K are much more impacted as the apparent pKa2 (HCO3 -CO3 2-) is shifted down from 10.3 to 6. P ssNMR data at -120°C and fitted using the Henderson-Hasselbach equation. The resulting apparent pKa values are indicated.