How to Convert Potassium Nitrate Into Ammonium Nitrate

Among its many uses, ammonium nitrate can serve as a fertilizer.

Ammonium nitrate is a salt compound derived from the combination of ammonia and nitric acid. It is often used to fertilize nitrogen-loving plants. Its chemical formula is NH4NO3. It is composed of clear crystals and has no odor. In addition to its gardening benefits, ammonium nitrate is also used to aid in the manufacture of various pyrotechnics, as well as solid rocket fuels. It is also used to treat titanium. It is highly combustible in the presence of heat, and can oxidize other flammable materials, so it is important to use care in its preparation and use.

Difficulty:

Moderate

Instructions

Things You'll Need

• 138 grams sodium bisulfate
• 300 ml water
• Additional water (separated)
• 101 grams potassium nitrate
• Ammonia
• pH meter or pH strips
• 500 ml methanol
• Coffee filters

1. Mix the sodium bisulfate in just enough water to dissolve it completely, which should be about 300 ml at the most.

2. Mix the potassium nitrate in as little water as necessary to fully dissolve it.

3. Combine the sodium bisulfate and potassium nitrate.

4. Add ammonia gradually until a pH of just above 7 is reached. This is the neutral point between acids and bases on the pH spectrum. You can add a little at a time and use pH strips to periodically check the pH, or you can leave a pH meter in the solution and watch the pH as you pour.

5. Remove the sodium bisulfate by boiling the mixture until you begin to see salts settle out of the mixture.

6. Freeze the compound overnight to further purge the solution of sodium bisulfate. Strain out the crystals with a coffee filter, reserving the liquid.

7. Let the liquid evaporate over several days to crystallize the ammonium nitrate.

8. Purify the ammonium nitrate further by adding 500 ml of methanol. Filter the solution again through coffee filters.

9. Allow the liquid to evaporate, again over several days. The remaining salt is ammonium nitrate.

References

• Chemical Land 21: Ammonium Nitrate
• NurdRage: How To Make Ammonium Nitrate
• Elmhurst College:Virtual Chembook--pH Scale