The Topley–Smith Effect

Abstract

An abnormal change of the dehydration rate, J, of crystalline hydrates with an increase of water vapour pressure, Pw, was discovered by Topley and Smith (T–S) in 1931 [1] in their studies of the dehydration rate of MnC2O4 2H2O. In contrast to the expected monotonous decrease of the rate with increasing Pw, the dehydration rate, on reaching a certain critical pressure (about 0.1 Torr), begins to increase, passes through a maximum (about 1 Torr), and then decreases (Fig. 7.1).