Start a Fire with a drop of Water

This is an old formula we used to make when we were kids.
We used to call it "Negative-X" (I have no idea why), but I'm sure it's known by other names.
When a drop of water touches a small pile of this mixture, it instantly bursts into a blue-green flame, accompanied by a large cloud of smoke. 

"NEGATIVE-X"
Ammonium Nitrate	14.0 grams
Ammonium Chloride	1.5 grams
Zinc Dust	34.5 grams

Comments:

Grind the Ammonium Nitrate and the Ammonium Chloride together in a mortar & pestle until they are a fine powder. Once the remaining chemical, Zinc Dust, is added, this composition will become extremely water sensitive. It is suggested that before you add the required amount of Zinc Dust, you move your experiment outdoors just in case accidental ignition occurs. As always, gloves and eye protection are called for.

Note that as soon as all the components are mixed, it will become extremely water sensitive!

Even a tiny amount of water will ignite the mixture. You must use this composition immediately
after it is made - DO NOT STORE IT - for any length of time, and do not mix it with other chemicals.
It's recommended to only mix this formula & conduct this experiment outside.

Take about a teaspoon full of the mixture and make a small pile of it on the ground. Make sure the ground is dry and that there are no flammable materials nearby (dry grass, paper, etc.).
Press a little indentation into the top of the pile and add a drop of water.
QUICKLY STAND BACK!
 In a second or so it will bubble, hiss and smoke, and instantly burst into a blue-green flame.

WARNING
Don't store this mixture, it will eventually absorb enough water from the air to ignite on its own.
Use all that you make each time.
Do Not make large quantities at one time.
This is NOT something you want to mix on a rainy day.

Here's the chemical reaction that takes place:

1. Cl- (from NH4CL) acts as a catalyst on the decomposition of NH4NO3:

Cl-

NH4NO3-----------------> N2O(g) + 2 (H2O)(aq)

2. Water in the reaction causes the decomposition of more NH4NO3, which is an autocatalytic effect.

3. The reaction melts the NH4NO3 and allows the oxidation of the zinc. The overall reaction is:

Zn (s) + NH4NO3 (s)------> N2 (g) + ZnO (s) + 2 (H2O) (g)