This demonstration effectively shows what happens when a cigarette is smoked. The diagram above shows how to set up the demonstration apparatus, although the equipment used may vary from school to school.
Equipment typically required (per demo):
- Large conical flask
- Universal indicator solution
- 2 pieces of bent glass tubing with relevant holed bungs
- Retort stands, bosses and clamps
- Wider glass tube with holed bungs
- Ceramic/cotton wool
- Water powered filter pump (or hand pump or gas syringe)
- Cigarette holder (or plastic tube)
This demonstration has been the subject of much discussion with the recent smoking ban coming into force in the UK. Please follow CLEAPSS or your local authority advice before using cigarettes in schools. Although it is generally accepted that this demonstration can be conducted within a fume cupboard in most regions, be aware that some, including Scotland, may have banned this demonstration altogether.
A cigarette is secured into the holder or plastic tube and lit. The filter pump draws air through the apparatus with the smoke from the lit cigarette passing through the large glass chamber depositing tar on the mineral/cotton wool. When the cigarette is completely burnt, the wool can be removed and shown to students. The typical aim of this demo is to show students how much tar is produced from a single cigarette. Some teacher may want to weigh the wool after the cigarette has been burned. Be aware that the glass tubes may remain hot after use.
The type of pump used can be either a water powered filter variety or hand drawn vacuum pump. If neither are available then a large gas syringe could be used. This will however draw significantly less air and would need to be removed and primed after each draw.
Another thing to watch for is that the long tube is below the level of UI solution with the shorter tube being above the level. This ensures that all of the gas from the cigarette passes through the solution and that no liquid is drawn into the filter pump.
After use, the equipment will smell very strongly and contain tars. Equipment should be cleaned before re-use using a solvent such as ethanol (flammable).
Gloves should also be worn when disassembling the equipment.
After several uses the glass tubes may become more and more opaque due to deposits on the internal surfaces. Excessive deposits may render the equipment fairly useless for observation purposes so be aware that replacement equipment may be required periodically.