Comprises a capillary tube, sealed at one end, with graduated scale from 0 to 200mm, mounted on a plastic former which also has a 0 ? 70?C thermometer mounted alongside the tube.The glass tube includes a small bead of coloured oil, which has already been injected into the tube at about the 50mm mark, and the back plate has a hole at the top to allow fixing to a retort stand, so that the?apparatus can be suspended in a tall beaker of water (not included). 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.Dimensions: Glass tube, 245mm long; Overall length, 350mm.Available individually or as a class set of 10 in a Gratnells tray.Replacement capillary tubes with oil beads are also available, sold as a pack of 10.