Weathering of Silicate Minerals : Influence of Chemical Agents on Them

Department of Applied Chemistry, Calcutta University, Calcutta Manuscript received 22 November 1971; accepted 9 July 1973 Three clay minerals belonging to illite, vermiculite and chlorite group were subjected to weathering treatments by 10% hydrochloric acid and Sodium tetraphenyl Boron salt treatments. X-ray diffraction patterns of the treated clays show changes in mineral structures. The treated clay lattice of illite is however not much affected by acid treatment except that the basal spacing shifts from 9.80Å to 9.77Å without change in intensity. Vermiculite on treatment with excess of 10% HCl results in collapse of mineral structure. A chloritic clay can stand weathering action of acid to a longer duration and shows no change in basal spacing. This difference in acid attack between Mite, vermiculite and chlorite has been correlated to their compositional differences in lattice substitution and charge distribution in the lattice. NaBPh4 treatments of illite and K-vermiculite show interesting changes, NaBPh4 treatment removed interlayer potassium from illite to a minor extent, 9.84 Å basal spacing shifts to 10.03 Å. The interlayer potassium content of K-vermiculite is easily removed within seven days causing an expansion of lattice from 10.1 Å to 14,71 Å