Solid-state reaction between thallous carbonate and iodine

Abstract

Iodine vapour reacts with solid thallous carbonate liberating carbon dioxide. A yellow coloured reaction product is formed which subsequently changes into a black one. The latter has been identified as Tl₂OI₂ which at higher temperature liberates oxygen and forms T1I. The crystal lattice of Tl₂OI₂ belongs to the orthorhombic system with a = 16·83 Å, B = 11·12 Å, C = 8·52 Å, and Z = 8. The pycnometric density, using cyclohexane as displacing liquid, has been found to be 5·617 ± 0·005 g/cm³ whereas the X-ray density is 5·653 g/cm³. The kinetics of the bulk diffusion of iodine in the solid has also been studied and a mechanism of propagation of the reaction is discussed.