"Mercury beating heart" experiment

How to make a mercury drop pulsate

In this ex­per­i­ment, a mer­cury drop starts pul­sat­ing quick­ly from the touch of an iron nail.

Reagents and equip­ment:

  • mer­cury;
  • 6M of sul­fu­ric acid;
  • potas­si­um bichro­mate;
  • iron nee­dle (nail).

Step-by-step in­struc­tions

Place a small drop of mer­cury care­ful­ly on a watch glass. Pour the 6M so­lu­tion of sul­fu­ric acid so that the mer­cury drop is com­plete­ly cov­ered with the liq­uid. Add a small amount of potas­si­um bichro­mate. Care­ful­ly touch the sur­face of the mer­cury drop with an iron nail, nee­dle or wire. The iron should be dipped in the sul­fu­ric acid. The end of the iron ob­ject should bare­ly touch the sur­face of the mer­cury drop. Ob­serve the mer­cury drop start to pul­sate.

Pro­cess­es de­scrip­tion

The mer­cury drop pul­sates as a re­sult of a change in sur­face ten­sion. In the acid which acts as an elec­trolyte, in the pres­ence of the ox­i­diz­er potas­si­um bichro­mate, the mer­cury on the sur­face of the drop ox­i­dizes, which caus­es a re­duc­tion in sur­face ten­sion com­pared with the un­ox­i­dized met­al. When the mer­cury makes con­tact with the met­al item, the iron re­duces the mer­cury on the sur­face, as a suf­fi­cient­ly neg­a­tive elec­tro­chem­i­cal po­ten­tial aris­es be­tween these met­als. When it is re­duced, the sur­face ten­sion of the mer­cury drop in­creas­es, and the drop con­tracts. This caus­es con­tact be­tween the mer­cury and the iron to break, the mer­cury is ox­i­dized again, the sur­face ten­sion de­creas­es, and the drop spreads out once more. As a re­sult, the drop touch­es the met­al again, and the cy­cle re­peats.

Safe­ty pre­cau­tions

Mer­cury is a very tox­ic sub­stance! Its fumes are poi­sonous! Don’t con­duct the ex­per­i­ment at home! Make sure the acid does not come into con­tact with the skin, and don’t let the sub­stances in the ex­per­i­ment near your eyes or mouth. Wear pro­tec­tive glass­es and gloves. Fol­low gen­er­al safe­ty rec­om­men­da­tions. Chem­i­cal ex­per­i­ments must be car­ried out in full com­pli­ance with the leg­is­la­tion of your coun­try, more safe ex­per­i­ments for kids you can fing through our chem­i­cal sets for kids month­ly sub­scrip­tion.

Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health. Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.