* This instrument is a gas law demonstrator for high school physics teaching demonstrations to verify Boyle-Marriott law, Charles' law, Guy Lussac's law, ideal gas state equation * The demonstrator is composed of main components such as air column glass tube, pressure gauge, constant volume mechanism, fixed frame and volume ruler. * The volume and pressure of the gas can be read from the volume scale and the scale of the pressure gauge. The gas volume is changed by pulling the pipe plug by hand. The rotation of the pressure gauge pointer indicates that the gas pressure also changes. In this way, when the temperature is constant, the relationship between the pressure P and the volume V (Boyle-Marzhao's law) is obtained. * If you need to change the temperature of the gas to be measured, the gas column glass tube of the demonstrator must be immersed in a beaker containing hot water to obtain the relationship of P, V, and T (gas equation). * When keeping the volume V or the pressure P constant, the Charlie's law or the Guatezach's law can be verified.