Ammonia gas is toxic and corrosive. This demo must be prepared in the hood.
Chemicals and Solutions
- Lecture bottle of anhydrous ammonia
- Bromocresol purple indicator
- Tech Notes: Chem 317 tech may have lecture bottles of NH₃ or HCl available (rather than storing extra bottles of this in the demo lab)
- Fountain set-up, see photo
- 2 mL disposable plastic pipet
- Two pinch clamps
- Vacuum grease for seals
- The upper bulb of the apparatus must be DRY prior to filling with ammonia.
- Carefully disassemble apparatus.
- Fill the bottom flask with water and color with bromocresol indicator solution. Make the water in the flask yellow by adding dilute HCl until the solution just changes color.
- In the hood, connect lecture bottle of ammonia and flush upper flask with plenty of gas. All air must be displaced and a certain amount of mixing of the gases must be overcome. (Do not fill more than 3 hours before intended use.) Keep the bulb opening facing down.
- After shutting off tank valve on lecture bottle, seal the upper bulb with a solid rubber stopper until demonstration time.
- At demonstration time, quickly swap out the solid rubber stopper with the two-hole stopper that has the hollow glass tube already connected. KEEP THE BULB OPENING FACING DOWN.
- Fill the disposable pipet with water, then quickly jam into the other hole of the rubber stopper (jam to ensure a good seal) and squeeze the water out. The fountain should immediately start.