• Respirometers are used to measure and investigate the?rate of oxygen consumption?during aerobic respiration in organisms
• The experiments usually involve organisms such as seeds or invertebrates

Apparatus

• Respirometer
• Glass beads
• Germinating seeds
  • These will be actively respiring and consuming oxygen
• Test tubes
• Soda-lime pellets (or potassium hydroxide)
  • To absorb the carbon dioxide produced
• ?Stopwatch

A respirometer set up to measure the rate of respiration

Method

• Measure oxygen consumption: set up the respirometer and run the experiment with both tubes for a set amount of time (e.g. 30 minutes)
• As the seeds consume oxygen, the?volume of air?in the test tube?will decrease?(CO2?produced during respiration is absorbed by soda lime or KOH)
• This?reduces the pressure?in the capillary tube and?manometer fluid will move towards?the test tube containing the seeds
• Measure the distance moved by the liquid in a given time
• Use this measurement to calculate the change in gas volume within a given time,?x?cm3?min-1
• Reset the apparatus: Allow air to re-enter the tubes via the screw cap and reset the manometer fluid using the syringe
• Repeat?experiment several times and calculate the?average volume of oxygen consumed

Calculations

• The volume of oxygen consumed (cm3?min-1) can be worked out using:
  • The diameter of the capillary tube?r?(cm)
  • The distance moved by the manometer fluid?h?(cm) in a minute using the formula:

πr2h