How to ignite zinc with just a drop of water ("Negative X")

This explosive detonates from a waterdrop

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves, a mask, and safe­ty glass­es. Con­duct this ex­per­i­ment in a well-ven­ti­lat­ed area. The re­ac­tion mix­ture is very sen­si­tive to mois­ture and is too dan­ger­ous to store.

Reagents and equip­ment

  • 8 g of zinc pow­der;
  • 8 g of am­mo­ni­um ni­trate;
  • 1 g of am­mo­ni­um chlo­ride;
  • a beaker;
  • a stir­ring rod;
  • a pipette;
  • wa­ter;
  • a fire­proof workspace

Step-by-step in­struc­tions

In the beaker, thor­ough­ly mix 8 g of zinc pow­der, 8 g of am­mo­ni­um ni­trate, and 1 g of am­mo­ni­um chlo­ride. Pour the mix­ture out onto a fire­proof sur­face and add a drop of wa­ter. The mix­ture will burst into a whirl­wind of smoke and blue-green flame!

Process de­scrip­tion

A mix­ture of zinc pow­der, am­mo­ni­um ni­trate, and am­mo­ni­um chlo­ride is of­ten called “Neg­a­tive X.” Adding just a small drop of wa­ter ini­ti­ates a re­dox re­ac­tion, which is sped up by the pres­ence of chlo­ride ions. Be­ing a strong re­duc­ing agent, zinc re­acts ex­plo­sive­ly with ni­trate ions to pro­duce zinc ox­ide, ni­tro­gen, and wa­ter:

NH₄NO₃ + Zn = ZnO + N₂ + 2H₂O