“Detonation by water” experiment

How to ignite magnesium powder and silver nitrate with a water drop

A spec­tac­u­lar chem­istry ex­per­i­ment with deep his­tor­i­cal roots.

Safe­ty pre­cau­tions

Safe­ty rules must be ob­served when work­ing with ex­plo­sive sub­stances and mix­tures.

Reagents and equip­ment:

  • sil­ver ni­trate (2 g);
  • mag­ne­sium pow­der (2 g);
  • wa­ter;
  • pipette;
  • beaker.

Step-by-step in­struc­tions

In the beaker, we mix mag­ne­sium pow­der and sil­ver ni­trate in the pro­por­tion of 1:1. Then we drip wa­ter on to the re­sult­ing mix­ture – it bursts into flame!

Pro­cess­es de­scrip­tion

Mag­ne­sium is a very re­ac­tive met­al, so it forces less re­ac­tive met­als out of their salts (for ex­am­ple from sil­ver ni­trate). Wa­ter is the ini­tia­tor of this re­ac­tion. Sil­ver ni­trate dis­solves in wa­ter, and mag­ne­sium forces sil­ver out of its salt. In the course of the re­ac­tion, heat is re­leased, which is suf­fi­cient for the break­down of sil­ver ni­trate into ni­tro­gen (IV) diox­ide, metal­lic sil­ver and oxy­gen, which ox­i­dizes metal­lic mag­ne­sium. A large amount of heat and light are re­leased. This prop­er­ty of the re­ac­tion of mag­ne­sium with any ox­i­diz­ers was used in the first cam­era flash­es. But this mix­ture is very dan­ger­ous, as the mois­ture in the air can eas­i­ly set off the re­ac­tion:

2Mg + 2Ag­NO₃ = 2MgO + 2NО₂ + 2Ag

2Ag­NO₃ = 2NО₂ + 2Ag + О₂