Ammonium nitrate is a chemical compound used in agriculture and to make pyrotechnics or cold packs or to perform other interesting demonstrations. It’s also used to create controlled explosions in mining and quarrying. It was once mined as a natural mineral in the deserts of Chile, but it is no longer available except as a man-made compound.
While it is not difficult to make ammonium nitrate, be advised it is dangerous to do so as the chemicals involved can be hazardous. In addition, ammonium nitrate becomes explosive when mixed with fuels or other chemicals.
OPTIONS FOR OBTAINING AMMONIUM NITRATE
You can make ammonium nitrate from common household chemicals. Keep in mind, though, that you can buy ammonium nitrate as a pure chemical; alternatively, you can collect it from instant cold packs or some fertilizers more easily and inexpensively than making it yourself. The easiest way to make ammonium nitrate is simply by reacting nitric acid with ammonia, but if you don’t have access to nitric acid (or don’t want to work with such a dangerous chemical), you can make ammonium nitrate from readily available home chemicals.
HOW TO MAKE AMMONIUM NITRATE
The chemicals used in this project are smelly and corrosive, so this project should be performed under a fume hood or outdoors. As always, wear gloves, eye protection, and appropriate clothing.
Some of the reagents and the final product are flammable or are oxidizers, so keep the chemicals away from open flames.
- 138 g sodium bisulfate (found with pool chemicals, used to lower pH)
- 1 mole equivalent of a nitrate salt, available as any of the following:
- 85 g sodium nitrate (common food preservative)
- 101 g potassium nitrate (which you can buy or make yourself)
- 118 g calcium nitrate (tetrahydrate)
- ammonia (common household cleaner)
- methanol (optional, which may be found as HEET fuel treatment)
- pH meter or pH paper
- access to a stove
- coffee filter or paper towels
- Dissolve the sodium bisulfate in the minimum amount of water (about 300 ml).
- Dissolve your nitrate salt in the minimum amount of water (amount depends on the salt).
- Mix the two solutions.
- Next, you will neutralize the solution, which is quite acidic. Stir in ammonia until the pH of the mixture is 7 or higher. Use a pH meter (or pH paper). Reacting ammonia, sodium bisulfate, and nitrates will give you sodium sulfate and ammonium nitrate.
- Sodium sulfate and ammonium nitrate have different solubilities in water, so boil the solution to get the sodium sulfate to crystallize. Remove the liquid from heat when crystals of sodium sulfate form in the bottom of the pan.
- Chill the solution in the freezer to get as much of the sodium sulfate as possible to drop out of the solution.
- Run the solution through a filter (coffee filter or paper towels) to separate the solid sodium sulfate from the ammonium nitrate solution.
- Allow the ammonium nitrate solution to evaporate, which will give you ammonium nitrate, with some sodium sulfate impurity. This is ‘good enough’ for most chemistry projects.
- If you want to further purify the ammonium nitrate, dissolve it in about 500 ml of methanol. The ammonium nitrate is soluble in methanol, while the sodium sulfate is not.
- Run the solution through a filter, which will give you sodium sulfate on the filter and a solution of ammonium nitrate.
- Allow the methanol to evaporate from the solution to obtain crystalline ammonium nitrate.