Barite (BaSO4) was synthesized at normal pressure and room temperature by m
ixing sodium sulfate and barium chloride solutions by gentle flow (0.5 ml/m
in.). The well-formed rectangular and rhombohedral crystals with smooth fac
es formed from solutions with low degrees of supersaturation. Most precipit
ates became single crystals. We employed the scanning electron microscope (
SEM) to observe barite dissolution by chemical agent diethylenetrinitrilope
ntaacetic acid. Molecular modeling was used to assist the interpretation of
the surface reaction. A kinetic model for the pit growth (initial dissolut
ion) on the surface was evaluated. With SEM microanalysis of barite and kin
etic model of pit growth, important surface phenomena and mechanisms of dis
solution can be hypothesized. Surface phenomena and composition are very im
portant in barite dissolution. Experimental results suggest that the initia
l dissolution starts on the two lowest energy surfaces: (001) and (210), an
d that the etch pits are elongated in one direction on the (210) surface an
d formed cavities on the (001) surface. The simulated surface structures by
molecular modeling can aid the interpretation the pit formation on those s
elected surfaces. (C) 1999 Academic Press.