Ammonia Fountain
Behold the amazing power of the vacuum!
Chemicals and Equipment Needed
 d-H2O
 Squeeze bottle of d-H2O
 4 L beaker, labeled “Ammonia Fountain” – Z
o Phenolphthalein (as needed) – N1
 Cylinder of NH3 – hood
 2 L round bottom flask and cork ring – Q5
 Special stopper for round bottom flask – P5
o With glass tubes and tygon tubing
 50 mL beaker – P4
o Contains 2 small red serum stoppers and 1 small pipet bulb
 Tall ringstand
 Large (fixed) iron ring, covered in parafilm – J2
Preparation – this demo is usually kept on the cart
 WARNING: When the demo is done, the apparatus will be extremely top-heavy. Never ever EVER try
and move it with the now-full RBF in a high position. Before moving, you must lower the iron ring, and
preferably remove the pipet bulb to start draining the flask. You will break the flask and other glassware
if you try and move the cart or apparatus without lowering the flask.
 If the solution in the “Ammonia Fountain” beaker is old or gross, make a new one:
o 3.5 L d-H2O and ~8mL phenolphthalein.
 The flask must be dry. If you have to do this several times in one day, rinse the flask with acetone and
use the air hose to dry it.
 Insert the special stopper into the neck of the flask and wrap parafilm around it to secure it. Set it on
the cork ring in the hood. Connect the hose from the NH3 cylinder to the short glass tube in the stopper.
Make sure to arrange the tygon tubing so that the gas flows away from you. Open the cylinder with the
provided cylinder wrench, then partially open the hand valve. Test for gas flow by holding a piece of
pink litmus paper at the opening of the tygon tubing; if it turns blue, gas is flowing. You may want to
wear gloves for this.
 Allow gas to flow for 2 minutes, then close the hand valve. Close the cylinder, then reopen the hand
valve to bleed out any remaining gas, and close again. Plug the end of the tygon tubing with the red
stopper, then remove the gas tube and plug the glass tube with the other red stopper.
 Set the beaker on the base of the ringstand, and the flask on the cork ring next to it.
 On delivery: Turn the flask upside down and place it (neck down) in the iron ring. Put the tubing in the
large beaker, and remove the stopper (ask instructor if that’s ok). Make sure the tubing runs along the
inside of the beaker and won’t get stuck on the side of the beaker.
 Use the squeeze bottle to fill the pipet bulb. Remove the other red stopper, and attach the bulb to the
short glass tube.
Revised Spring 2015
AMM
Presentation
 Squeeze the bulb to force water into the flask. Due to significant hydrogen bonding, the NH3 will
immediately begin dissolving in the water, which creates a partial vacuum. Ambient atmospheric
pressure pushes the water from the beaker into the flask, creating a fountain effect. Additionally, the
basic NH3 solution turns the solution bright pink.
 The effect will continue until the pressure is equalized (the flask will be nearly full)
 The reaction is:
NH3 (g) + H2O (ℓ) → NH4OH (aq)
Clean-Up
 Lower the flask until it is just above the beaker. Remove the pipet bulb and allow the flask to drain as
much as it can. Remove the flask from the iron ring, take out the stopper, and wash the whole
assembly, using the air spigot in the hood to dry the glass and tygon tubing. The round bottom flask
generally takes 1-2 days to dry; you can speed it up by running air through it, again from the spigot in
the hood, or rinsing with acetone.
 Carefully add 6 M HCl to the large beaker until colorless. (This typically takes ~10-30mL) Reuse the
liquid in the beaker until until the water/phenolphthalein solution looks gross.
 Note: if you have to add a lot of HCl (more than 30 mL), you will want to make a new beaker of solution.
NOTES: For another way to harness the power of the ammonia fountain, see Luminol Ammonia Fountain
Revised Spring 2015
AMM