A lot of readers have asked me where they can find potassium nitrate or saltpeter, which is a common ingredient in many pyrotechnic recipes and other home science projects. Your two choices are purchasing it or making it from other chemicals.
Get Potassium Nitrate from a Store
The answer: stump remover. Spectracide’s Stump Remover is potassium nitrate. In the United States it can be purchased at Lowe’s or Home Depot, among other places. Also, you can make potassium nitrate yourself from salt substitute and a cold pack.
Make Your Own Potassium Nitrate
To make potassium nitrate, you need:
- 40 grams ammonium nitrate
- 37 grams potassium chloride
- 100 milliliters water
The ammonium nitrate comes from a cold pack that lists it as an ingredient. It’s the packet of granules or crystals. Potassium chloride is sold as a salt substitute. Make sure it’s listed as the only ingredient.
The chemical reaction to make the potassium nitrate is:
NH4NO3 + KCl → KNO3 + NH4Cl
- Dissolve the ammonium nitrate in the water.
- Filter the solution through a coffee filter to remove particulates.
- Add the potassium chloride and gently heat the solution to get the salt to dissolve. Don’t boil it.
- Again, filter through a coffee filter to remove solids.
- Place the liquid in a freezer or on ice. The potassium nitrate will crystallize out of the solution.
- Pour off the liquid to get the potassium nitrate crystals. They won’t be absolutely pure, but will work for most chemistry demonstrations and pyrotechnics projects. If you like, you can evaporate the water out of the liquid to recover the ammonium chloride, too. Both chemicals are useful for science projects.
Potassium Nitrate Project Ideas
Once you have potassium nitrate, here are some projects to try:
- Make a Smoke Bomb
- Make a Homemade Firecracker
- Fire Writing
- Make Homemade Sparklers
- Make a Weather Glass
- Dancing Charcoal Chem Demo