The anion-exchange reaction of the layered. a-cobalt hydroxides Co(OH)(1.75)(DDS)(0.25)center dot 0.6H(2)O (1) and Co(OH)(1.7)Cl-0.3 center dot 0.4H(2)O (3) with carbonate has been investigated. For 3 the reaction proceeds by complete displacement of the interlayer Cl- anions by CO32- to give Co(OH)(1.7)(CO3)(0.15)center dot 0.6H(2)O (4). Remarkably for 1 we only observe ion-exchange of the DDS- from every other layer to give the second stage intercalate Co(OH)1.75 (DDS)(0.07)(CO3)(0.09) center dot 0.5H(2)O (2). The kinetics of these processes have been investigated using time-resolved in situ energy dispersive XRD and small/wide-angle X-ray scattering. In both cases the reaction order (n) was found to be consistent with a two-dimensional diffusion controlled models Both 3 and 4 are magnetically ordered, and dc and ac magnetic susceptibility measurements have been used to explore their 3D ferrimagnetically ordered ground states.