Controlled addition of impurities

Doping of solid reactant involves the introduction of a controlled amount of an impurity into solid solution in the host lattice. Such impurities can be selected to cause the generation or destruction of those electronic or structural defects which participate in the rate process of interest. Thus, the influence of the additive on kinetic behaviour can provide evidence concerning the mechanism of reaction [46,47]. Even if the 

There have been many instances of examination of the effect of additive product on the initiation of nucleation and growth processes. In early work on the dehydration of crystalline hydrates, reaction was initiated on all surfaces by rubbing with the anhydrous material [400]. An interesting application of the opposite effect was used by Franklin and Flanagan [62] to inhibit reaction at selected crystal faces of uranyl nitrate hexa-hydrate by coating with an impermeable material. In other reactions, the product does not so readily interact with reactant surfaces, e.g. nickel metal (having oxidized boundaries) does not detectably catalyze the decomposition of nickel formate [222], 

When a reactive atmosphere is present [402,1249], the reaction undergone by a solid may be changed, and perhaps complicated, by the presence of a concurrent or consecutive gas—solid reaction. When one or more of the products of the reaction in vacuum is an oxidizable metal [60] or 

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