 In a demonstration to show a solution catalyst, we will heat a solution of sodium potassium tartrate. We will add a solution of hydrogen peroxide. The reaction is very slow initially, even at 60 degrees Celsius. We will then add some cobalt plus 2 ion. The cobalt ion forms a complex ion with a tartrate ion. The solution turns green due to the formation of this complex ion. The reaction becomes very rapid. We see the evolution of carbon dioxide gas. At the end of the reaction, the solution turns back to pink, showing the regeneration of the catalyst.