This demonstration shows why it is important to waft chemical vapors instead of smelling them directly. Ammonia vapor rising from an ammonium hydroxide solution is detected by phenolphthalein-treated paper, which turns pink in the presence of the base.

1. Soak a piece of filter paper in phenolphthalein solution and allow it to dry in a fume hood overnight.
2. Swirl a bottle of ammonium hydroxide gently to build pressure.
3. Open the bottle slowly to release ammonia vapor.
4. Hold the dried filter paper with forceps and pass it above the mouth of the bottle.
5. Observe the filter paper turn pink as ammonia vapor diffuses into it.
6. Demonstrate the wafting motion with your hand to show how odors should be tested safely.

Wafting - Josh Thomas:

📄 Waft It — Don’t Sniff It! - Flinn Scientific: https://www.flinnsci.com/api/library/Download/47890af9c0ad488c955c2671f48b1dbb?srsltid=AfmBOormNn8d0MNPFIjY8Twl06o9orcuRTYlyKn5xcG4twkpM-prRdyH

• Try using other pH indicators (e.g., universal indicator paper) to detect ammonia vapors.
• Place treated paper at different heights above the bottle to demonstrate diffusion.
• Compare ammonia with other safe household vapors (e.g., vinegar) to illustrate differences.

• Ammonium hydroxide vapors are highly irritating and toxic - never inhale directly.
• Wear chemical splash goggles, gloves, and a lab apron.
• Conduct the experiment in a fume hood or well-ventilated area.
• Handle phenolphthalein solution with care; it is flammable and moderately toxic.
• Dispose of waste materials following appropriate chemical disposal guidelines.

• Why is it dangerous to sniff chemicals directly? (Some vapors are toxic or can damage nasal passages.)
• What is the purpose of wafting? (It allows controlled detection of an odor while minimizing exposure.)
• Why does the phenolphthalein paper turn pink? (Ammonia vapor dissolves in the moist paper, raising the pH and causing the indicator to change color.)
• How does molecular weight affect gas diffusion? (Lighter gases diffuse faster through air than heavier ones.)