Decomposition of sodium potassium tartrate by hydrogen peroxide in the presence of the catalyst cobalt(II)chloride

The image shows a heated colourless solution of sodium potassium tartrate and hydrogen peroxide. Click to see what happens when an cobalt(II) chloride solution(pink colour!) is added!

Notice that during reaction the colour has changed to green, gas is liberated, cobalt(II) chloride is restituted at the end of reaction (pink colour!)

Video adapted from Interconnectome