Table 3.

Water surface density, $n_{H_{2}O}$ (given as water molecules per nm²) for the two hydration conditions considered.

Materials	${\mathit{n}}_{{\mathit{H}}_{\mathit{2}}\mathit{O}}$, (fraction irreversible by outgassing at 323 K)	${\mathit{n}}_{{\mathit{H}}_{\mathit{2}}\mathit{O}}$, (fraction reversible by outgassing at 323 K)
HA1	4.4 ± 0.5	8.2 ± 0.7
HA2	4.1 ± 0.5	8.4 ± 0.7
Cit–HA–4 h	7.9 ± 0.7	6.3 ± 0.6
Cit–HA–24 h	3.1 ± 0.4	5.8 ± 0.6
Cit–HA–96 h	3.5 ± 0.4	4.6 ± 0.5