The behavior of ZSM5 zeolites in the acid, sodium form or ion-exchanged with various metal ions (Cs, Sr, Ba, Mg, Fe, Co, Cu, Ag, Rh, Ga, In, La, and Ce) and that of Y and X zeolites ionexchanged with Ba ions are discussed with reference to their behavior in the adsorption of N 2 O from gaseous industrial streams containing low (<0.1-0.2%) concentrations of N 2 O, to produce a concentrated (>5%) stream of N 2 O for either autothermic operation of the decomposition of N 2 O or use of N 2 O as a selective oxidant. Ba-ZSM5 show significantly better performances than other metal-exchanged zeolites in the adsorption of N 2 O, although water competes with N 2 O for adsorption. However, the adsorption of N 2 O is faster than that of water, and thus it is possible to adsorb N 2 O even in the presence of larger (40 times higher) amounts of water in the feed. It is also shown that it is possible to have a dual-bed selective adsorption, where first water adsorbs selectively on an alumina bed and then N 2 O is adsorbed on a Ba-ZSM5 bed. It is suggested that the enhanced adsorption properties of Ba-ZSM5 are related to the presence of naked Ba 2+ ions that creates a strong electrostatic field within the zeolite cavities which allows the orienting of the N 2 O molecule and its trapping inside the zeolite.

Summary. The X-ray diffraction method based on pole figures has been applied to single osteon samples in order to obtain information about the texture of the inorganic bone fraction and the way it changes during calcification. The osteon samples were cylindrically shaped, with axes corresponding to those of the haversian canals. Selection was carried out according to the degree of calcification and the orientation of collagen bundles and inorganic particles. Osteons at both the initial and final stages of calcification were chosen. Arrangements of fiber bundles and inorganic particles in successive lamellae characteristic of three types of osteons were selected: longitudinal, alternate, and transversal. The results indicate that in all three types of osteons, the long axis of the sample is apparently the only direction of orientation because the transversally oriented crystallites give an isotropic diffuse scattering as would be expected if all the inorganic particles were irregularly oriented around the osteon axis. The number of longitudinally oriented crystallites increases progressively from transversally oriented osteons to alternately and longitudinally oriented ones. The crystallite orientation in an axial direction increases in fully calcified osteons. This last result is in agreement with the electron microscopic finding that the long needleshaped crystallites covering much more than a major collagen period and measuring 40-45 A in width increase in number as calcification proceeds.