COMPLEXES BETWEEN LAMELLAR STRUCTURES AND BROMINE, IODINE CHLORIDE, AND CHROMYL CHLORIDE

Isotherms of Br2 on four sizes of natural graphite crystals were measured with a recording vacuum balance. For 0.02- to 2-mm crystals, capillary condensation near saturation was small but significant, surface adsorption was negligible, and the composition C16Br2 was independent of pressure from 0.9 to 0.5. For the 0.002- to 0.01-mm crystals capillary condensation near saturation and surface adsorption were much greater, there was less intercalation than in the larger crystals, and there were no pressure-independent compositions. These effects of crystal size on the isotherm are believed to account for many of the variations in the reported compositions of lamellates in general and show that the complete isotherm on natural crystals at least 0.02 mm across should be determined. When this was done, there were pressure-independent compositions of C16Br2, C16ICl, C8ICl, and about C40CrO2Cl2. In the latter case the longer the intercalated material remained in the structure the less of it diffused out on reduci...