THE CRYSTAL-STRUCTURE OF THE SODIUM OXOHY DROXOALUMINATE HYDRATE NA-2[AL2O3(OH)(2)]CENTER-DOT-1.5H(2)O

The crystal structure of the sodium oxohydroxoaluminate hydrate Na-2[A l2O3(OH)(2)]. 1.5 H2O (up to now described as Na2O . Al2O3 . 2.5 H2O a nti Na2O . Al2O3 . 3H(2)O, respectively) was solved. The X-ray single crystal diffraction analysis (tetragonal, space group P-42(1)m, a = 10 .522(1) Angstrom, c = 5.330(1) Angstrom, Z = 4) results in a polymeric layered structure, consisting of AlO3/2(OH) tetrahedral groups. Betwe en these layers the Na+ ions are situated, which form tetrameric group s of face-linked NaO6 octahedra. The involved O2- ions are due to Al-O -Al bridges, Al-OH groups and water of crystallization. Al-27 and Na-2 3 MAS NMR investigations confirm the crystal structure analysis. The r elations between the crystallization behaviour of the compound and the constitution of the aluminate anions in the corresponding sodium alum inate solution and in the solid, respectively, are discussed.