The role of dislocations in the dehydration of nickel sulphate hexahydrate. Part II. Topographical studies by use of optical microscopy

Dehydration patches, produced in the range 35–50°in vacua of ca. 1 µtorr, are not nucleated at random over the (00l) faces of α-NiSO4,6H2O but are preferentially formed at dislocations of both screw and edge character. Their number remains essentially constant as reaction proceeds in the initial stages. Patches are also formed readily at cleavage steps and at non-cleavage faces of type (hk0). The significance of these results is discussed.