Association Moléculaire et Paire Ionique dans le Verre et le Liquide du ‘Monohydrate de l'Acide Nitrique’

The Raman spectra of the equimolecular mixture HNO 3 ·H 2 O in the liquid and glassy states have been investigated in the range 4000–50 cm −1 . At least four species have been characterized: (i) The free molecular association H 2 O…HONO 2 ν OH (H 2 O) = 3550 cm −1 (3440 cm −1 ) and ν OH (HNO 3 ) = 2930 cm −1 (2915 cm −1 ) respectively in the liquid (and the glass). (ii) The free ionic pair (H 2 OH) + …(ONO 2 ) − that give a splitting (Δν = 170 cm −1 ) of the ν 3 (NO   3 − ) vibration. (iii) Free HNO 3 molecules: ν NOH = 940 and 950 cm −1 respectively in the liquid and the glass. (iv) The ‘nitric acid trihydrate’: H 7 O   3 + NO   3 − ν OH between 3100 and 3300 cm −1 .