Comprises a capillary tube, which is sealed at the bottom, having a graduated scale from 0 to 200mm. This is mounted onto a metal former which also has a -10 _ 100°C thermometer mounted alongside the tube. The overall length is 350mm with a hole at the top to affix to a retort stand to suspend the apparatus in a tall form beaker of water (not supplied). By heating the water and taking a temperature and scale reading every 30 seconds, a graph of the results can be plotted.
Through a line of best fit and extrapolation absolute zero can be demonstrated. The straight line supports Charles′ Law demonstrating that volume of a gas is directly proportional to its temperature provided the pressure is kept constant. (In this case the pressure is atmospheric pressure). The Kelvin scale may then be introduced.