“Mercury heart” experiment

How to make a mercury drop throb like a heart

Can you bring met­al to life? In this ex­per­i­ment, you’ll see how one touch to a drop of mer­cury makes it throb like a heart.

Safe­ty pre­cau­tions

Mer­cury is a very tox­ic sub­stance, and its fumes are poi­sonous! Don’t con­duct this ex­per­i­ment at home! Avoid ex­pos­ing skin to acid and keep the sub­stances in the ex­per­i­ment away from the eyes and mouth. Wear pro­tec­tive glass­es and gloves. Fol­low gen­er­al safe­ty rules. Con­duct­ing chem­i­cal ex­per­i­ments should ful­ly com­ply with the leg­is­la­tion of your coun­try.

Warn­ing! Don’t try to re­peat this ex­per­i­ment with­out a pro­fes­sion­al su­per­vi­sion!

Reagents and equip­ment

  • drop of mer­cury;
  • 5mL di­lut­ed sul­fu­ric acid;
  • 5mL potas­si­um dichro­mate so­lu­tion;
  • iron nail;
  • Petri dish.

Step-by-step in­struc­tions

Care­ful­ly place a small drop of mer­cury in a Petri dish. Pour the sul­fu­ric acid so­lu­tion over it. Add a lit­tle potas­si­um dichro­mate. Care­ful­ly touch the sur­face of the mer­cury drop with an iron nail, nee­dle, or wire. The iron ob­ject should be in the sul­fu­ric acid and bare­ly touch­ing the met­al drop. The mer­cury drop will start to throb like a heart.

Pro­cess­es de­scrip­tion

The throb­bing is con­nect­ed to a change in the sur­face ten­sion of the drop. In the so­lu­tion of potas­si­um dichro­mate, the mer­cury ox­i­dizes, and a film of mer­cury(I) sul­fate Hg₂­SO₄ forms on its sur­face. As a re­sult, the sur­face ten­sion of the mer­cury is re­duced and the drop ex­pands.

2Hg + SO₄²⁻ → Hg₂­SO₄ + 2e⁻

Cr₂O₇²⁻ + 14H⁺ + 2e⁻ → 2Cr³⁺ + 7H₂O

When the iron nail touch­es the drop, an ox­i­da­tion-re­duc­tion re­ac­tion oc­curs. The iron dis­solves and the mer­cury(I) sul­fate re­duces to metal­lic mer­cury. As a re­sult, the sur­face ten­sion of the drop in­creas­es again, it con­tracts, and the con­tact with the iron is lost.

Hg₂­SO₄ + 2e⁻ → 2Hg + SO₄²⁻

Fe → Fe²⁺ + 2e⁻

hen the sur­face of the mer­cury is ox­i­dized again, the drop is once again cov­ered with a lay­er of sul­fate, it ex­pands and touch­es the nail again. The process re­peats, and the drop throbs like a heart!