Application of the B.E.T. method to differentiating manganese dioxide modifications

Manganese dioxide samples belonging to the α-, γ- and δ-groups have been subjected to surface area measurements (B.E.T. method) and X-ray examination before and after heat treatment at 350 and 450°c. The change in surface area of the different samples is explained in terms of two processes which act in opposite ways, namely, creation of pores and cavities (left by the escaping water), and crystal growth. The surface areas of some local and imported natural samples of manganese dioxide as well as the β-group have been also determined.