ON THE CRYSTAL-CHEMISTRY OF NAP ZEOLITES

Multiphase samples containing a series of well-crystallized gismondine -type NaP zeolites, unit cell content Na xAlxSi16-xO32.yH2O with 3 les s-than-or-equal-to x less-than-or-equal-to 8, were prepared at 90-95-d egrees-C or 150-degrees-C from aluminosilicate glasses and aqueous sod ium hydroxide. Powder X-ray diffraction using a Guinier-Hagg camera an d energy dispersive X-ray microanalysis performed in a scanning electr on microscope revealed three NaP phases with increasing silicon conten t, i.e., low-silica P (8-10 Si atoms per unit cell), orthorhombic medi um-silica P (10-12 Si/cell), and tetragonal high-silica P (12-13 Si/ce ll). NaP1 (pseudocubic lattice geometry) probably represents an end-me mber low-silica P with 10 Si/cell, whereas NaP2 (pseudotetragonal latt ice geometry) is identical to medium-silica P.