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Ammonia Fountain

Empty set up of a round flask secured upside down by a ring stand, sealed with a two-hole stopper. Below the round flask is a large Erlenmeyer flask. A long glass tube runs from the Erlenmeyer into the round flask through one of the two rubber holes.

Hazards

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 NH or HCl available (rather than storing extra bottles of this in the demo lab)

Materials

  • Fountain set-up, see photo
  • 2 mL disposable plastic pipet
  • Two pinch clamps
  • Vacuum grease for seals

Procedure

  1. The upper bulb of the apparatus must be DRY prior to filling with ammonia.
  2. Carefully disassemble apparatus.
  3. 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.
  4. 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.
  5. After shutting off tank valve on lecture bottle, seal the upper bulb with a solid rubber stopper until demonstration time. 
  6. 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.
  7. 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.
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