Mercury beating heart

The beating mercury heart (also: vibrant mercury Heart) is an oscillating electrochemical redox reaction between the elements mercury, iron and chromium or manganese. By the reaction of a mercury droplet is caused to vibrate. The beating mercury heart in the form known today was first described by Fried Ferdinand Runge in 1829.

Experiment

For the experiment, one drop of mercury is placed in a watch glass and with an electrolyte such as sulfuric acid containing an oxidising agent such as hydrogen peroxide, potassium permanganate or potassium dichromate, overcoated. By the contact of the mercury drop from the side with the tip of an iron nail begins to pulsate this.

Mechanism

Upon contact of the mercury with the nail the less noble metal from iron are electrons. The mercury potty is negatively charged. Due to the repulsion between the electrons, the droplet assumes a spherical shape. Characterized contact is lost with the iron.

In the next step the charged mercury droplets reduces the present in the electrolyte solution permanganate or dichromate ions according to:

Or

By reducing the dichromate or of the Permangats Quecksilberröpfchen emits the electrons. This lowers the surface tension of the droplet and comes back in contact with the iron nail. Thus, the droplets begin to pulse and acts like a beating heart.

Although this reaction is mediated by changes in the surface tension, it is very similar to the other reactions, such as oscillating - Belousov Zhabotinsky reaction.