Solid state NMR as well as several other instrumental chemical analysis techniques were used in order to characterize two natural occurring bentonite. The methodology is described. The NMR spectra, together with the other used techniques suggest that the observed differences are due to iron inclusions in tetrahedral and octahedral sites 5 refs., 3 figs., 5 tabs.
Leite, Sidnei Q.M.; Dieguez, Lidia C;  Menezes, Sonia M.C.;  San Gil, Rosane A.S. 
- Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia
- PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas
- Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Quimica