Not every substance can accelerate any particular process.

    Therefore chemists say that catalysts are selective in their action: they may influence one reaction vigorously without paying attention at all to another. 

    Of course, there are exceptions to this rule. For example, aluminium oxide is capable of catalyzing several dozen different synthesis reactions of both organic and inorganic compounds. 

    Finally, different catalysts may make a mixture of the same substances react differently to form different products. 

    There are substances with no less surprising properties, called promoters. Taken by themselves, they do not influence the course of the reaction, neither accelerating nor decelerating it. 

    If added to a catalyst, promoters accelerate the reaction to a much greater degree than the catalyst itself. A platinum wire with "impurities" of iron, aluminium, or silicon dioxide, would cause a still more impressive effect in a mixture of hydrogen and oxygen.

    There is also another kind of catalysis, inside out catalysis. There are anticatalysis and anticatalysts. Scientists called them inhibitors. Their purpose is to slow down rapid chemical reactions.
 

---