What are the functions of the double walled glass tube in clinical thermometers?

The double-walled glass tube in clinical thermometers serves to enhance accuracy and stability in temperature readings. The outer wall insulates the inner tube, minimizing heat exchange with the environment and ensuring that the thermometer reacts primarily to the temperature of the substance being measured. Additionally, the design helps prevent the Mercury or alcohol column from falling back into the bulb after removal, allowing for a stable reading until the thermometer is reset. This construction improves the reliability and precision of the thermometer's measurements.