Frey Scientific Collapsible Can finds its use in demonstrating Charles' law and pressure principles. It can be hooked to a vacuum pump with a stopper, glass tube and vacuum hose to exhaust air and collapse the can. When a small amount of water is boiled in the gallon can steam pressure is obtained which is then trapped by closing the screw cap. During cooling, the condensing steam begins to lower the pressure inside the sealed can, but the external atmospheric pressure instantaneously crushes the can while the pressure remains constant. Capacity 1 Gallon.