HYDRATES OF WEAK AND STRONG BASES .11. - THE CRYSTAL-STRUCTURES OF NAOH.3,5H2O AND NAOH.7H2O - A REFINEMENT

The crystal structures of the hydrates NaOH . 3,5H2O (space group P2(1 )/c, Z = 8 formula units per cell; lattice parameters: a = 6.481, b = 12.460, c = 11.681 angstrom, beta = 104.12degrees at -100-degrees-C) a nd NaOH.7H2O (P2(1)/c, Z = 4; a = 7.344, b = 16.356, c = 6.897 angstro m, beta = 92.91-degrees at -150-degrees-C) have been redetermined usin g MoKalpha diffractometer data. The obtained refinement of the structu res, including the localization also of the H atoms for the first time , has led to new findings with respect to the H bonds. In particular, in both hydrates there is one such interaction of the rare type OH-... OH2, from an OH- ion to an H2O molecule, i.e. with the OH- ion as the proton donor.