It’s easy to make nitrous oxide or laughing gas at home or in the lab. All you need is a heat source and ammonium nitrate. Here are instructions to make nitrous oxide and tips for how to do it safely.
Laughing Gas Name
But first, you may be wondering why nitrous oxide is called laughing gas. British chemist Sir Humphry Davy coined the name, referring to the euphoric effects of inhaling the gas.
What Is Nitrous Oxide or Laughing Gas?
Nitrous oxide has the chemical formula N2O. It is a non-flammable, colorless gas that has a sweet flavor and slightly metallic scent. While its best-known use might be as an anesthetic, nitrous oxide has many other uses. It increases internal combustion engine power, serves as an oxidizer in chemistry experiments and rocketry, acts as a propellant for foods including cooking spray and whipped cream, and has multiple uses in medicine.
Make Nitrous Oxide
The simplest and safest method to make nitrous oxide at home or in a small lab is one devised by Humphry Davy. Davy discovered heating ammonium nitrate decomposes it into nitrous oxide and water vapor:
NH4NO3 (s) → 2 H2O (g) + N2O (g)
While simple, it’s important to gently heat the ammonium nitrate between 170 °C to 240 °C (338 °F to 464 °F). Exceeding the maximum temperature leads to rapid decomposition and will break the glassware. It’s safest to use small amounts of ammonium nitrate and either a thermometer or heat source with a thermostat to control the temperature.
- Place a small amount of ammonium nitrate in a test tube. Cap the test tube with a one-hole stopped. Insert plastic or glass tubing into the hole and run it into a hot water bath. The water needs to be hot because nitrous oxide dissolves in cold water, reducing the amount collected. Collect the bubbles in an inverted jar. This setup for collecting gases is called a pneumatic trough. It condenses water produced by the reaction and removes impurities, like smoke.
- Once you’ve set up the equipment, slowly heat the ammonium nitrate. You can do this over a flame or burner. Apply heat so that it does not exceed the maximum temperature and so it produces gas bubbles at the rate of one to two bubbles per second.
- Stop heating the ammonium nitrate before all of it has decomposed. This helps prevent overheating. Turn off the heat and disconnect the tubing from the collection jar so that water won’t flow up into it. Cover the container before turning it upright, so you won’t lose the gas. You can seal the container while it is inverted or simply cover it with a flat sheet of plastic or glass before turning it over. The gas in the container is nitrous oxide, plus smaller amounts of other nitrogen oxides, such as nitric oxide and nitrogen monoxide. Exposure to air oxidizes the nitric oxide to form nitrous oxide.
This procedure is used for the commercial preparation of nitrous oxide, with acid and base treatments to further purify the gas.
Here are tips to prepare nitrous oxide safely:
- Don’t heat ammonium nitrate over 240 °C or 464 °F.
- Stop applying heat before the last bit of ammonium nitrate has decomposed.
- Use the highest purity ammonium nitrate available. Pure ammonium nitrate is more stable than ammonium nitrate with impurities.
- Perform the project under a fume hood (in a lab) or in a well-ventilated area (at home). While nitrous oxide is a safe laboratory gas, overexposure via inhalation may cause hypoxia, much like overexposure to helium gas.
Other Ways to Make Nitrous Oxide
In 1772, Joseph Priestley became the first person to synthesize nitrous oxide. Priestly collected the gas produced by sprinkling nitric acid over iron filings. While an effective method, it’s best left to the lab rather than home because nitric acid should be used under a fume hood, with proper gear to protect against a splash.
Another method to make nitrous oxide in the home or lab is to heat a mixture of sodium nitrate and ammonium sulfate. Again, collect the gas using a pneumatic trough. Heating this mixture is even safer than decomposing ammonium nitrate.
2 NaNO3 + (NH4)2SO4 → Na2SO4 + 2 N2O+ 4 H2O
The chemical reaction between urea, nitric acid, and sulfuric acid also produces nitrous oxide.
2 (NH2)2CO + 2 HNO3+ H2SO4 → 2 N2O + 2 CO2 + (NH4)2SO4 + 2H2O
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