Calibrating a thermometer

We recently did a standard calibration exercise using melting ice and boiling water. We calibrated some alcohol-in-glass thermometers which had broken threads. Some things we learnt:

• make sure the thermometer is in good contact with the ice (well crushed ice is best)
• there is a small difference between the temperature of the steam and that of the boiling water
• the thermometers with the broken threads were several degrees in error for both fixed points

It was a useful activity and also teaches that instruments do not always give correct readings!