preproom.orgThe online science prep room
You are here: Home > Practicals > Rate of Diffusion

Rate of Diffusion
AKA: Ammonia Diffusion

Click for full size image
Click for full size image
Fig 1: Demo Equipment
Fig 1


Demonstration shows how ammonia diffuses in a sealed tube.


This demonstration shows how ammonia gas diffuses over time in a sealed tube. A glass tube needs to be prepared to house several strips of new litmus paper, held in place by attaching them to a length of cotton thread which is attached taut to each end of the tube. As the ammonia gas diffuses into the air in the tube, it will turn each piece of litmus paper blue as the gas is strongly alkaline.

The ammonia gas comes from a cotton wool pad soaked in ammonium hydroxide solution which is placed into a small hole created in one of the bungs. You should wear gloves when handling this cotton pad.

The greater the difference in concentrations, the greater the rate of diffusion in the tube. You should clearly see the litmus changing from a red to a deep blue as the gas diffused throughout the tube.

The diagram shows the demonstration equipment as it should be set up.


 CautionAmmonium hydroxide is harmful and corrosive.

Ammonia gas is toxic and irritant.

This demonstration should take place In a fume cupboard.

Wear eye protection.

Wear gloves when handling the ammonium hydroxide solution.

The contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.