Autocatalysis. Demonstration of autocatalysis using ethanedioate and manganate(VII) ions. Autocatalysis occurs when reaction products catalyse the reaction itself. In this case, a solution of potassium permanganate (purple) is added to a solution of ethanedioic acid (oxalic acid, colourless). One of the products, the manganese(II) ion, further catalyses the reaction, liberating large quantities of carbon dioxide and carbon monoxide gases.