1. Preheated solution of potassium sodium tartrate an hydrogen peroxide: A few gas bubbles show it is going on a very slow decomposition! 2. Addition of a solution containing rose coloured cobalt(II) ion $Co^{2+}$ . 3. The decomposition reaction is greatly accelerated! The green color shows that the cobalt(II) ion has turned into dirty green cobalt(III) ion $Co^{3+} $ . 4. At the end of the reaction, rose cobalt(II) ion is restituted. $Co^{2+}$ catalyses the decomposition reaction of tartrate.


The catalyst of a reaction is a chemical species that - accelerates the reaction. - is wholly restituted at the end of reaction.


- Catalysis accelerates the manufacturing of many substances essential to our industrial society and makes their production therefore profitable. The synthesis of sulfuric acid (200 million tonnes per year!) is accelerated for example by a vanadium compound. - Catalysis helps get rid of waste in our industrial society. Toxic exhaust of engines is eliminated through catalysts based on rhodium metal.