The Department of Chemistry at the University of Illinois

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Ammonia Fountain

inverted flask containing red liquid, ammonia gas dissolved in water

Why is water drawn up into the flask?

apparatus used

This picture shows the apparatus used in this demonstration. There is a beaker of water below and an inverted flask containing ammonia gas, NH3.

beaker of water and glass tube

The beaker of water and the flask of ammonia are connected by a glass tube that extends down into the water and up through the rubber stopper into the flask of ammonia. In this picture the end of the tube in the water is sealed with a small pipet bulb.

There is a second tube that extends through the rubber stopper that has a small pipet bulb filled with water.

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thumbnail of inverted flask

First, the small pipet bulb which seals the glass tube in the water is removed. Then, the small pipet bulb that is filled with water is squeezed so that the water it contains is pumped into the flask of ammonia gas.

inverted flask containing red liquid, ammonia gas dissolved in water

When water in the pipet bulb is squeezed into the ammonia gas, NH3 dissolves in the water.

NH3(g) + H2O(l) ----> NH4OH(aq)


When NH3 dissolves in the small amount of water squirted into the flask, it creates a vacuum which pulls water from the beaker below up the tube and into the flask of gas. More NH3 dissolves, which pulls more water from below. This creates a fountain effect. The pink color comes from phenolphthalein indicator in the water which is colorless until OH- ions are formed.

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Chemistry at Illinois University of Illinois at Urbana-Champaign