An alcohol thermometer is used to measure temperature and is an alternative to mercury thermometers. It is not recommended for precise measurements, because the alcohol may evaporate over time.
Alcohol is contained in a bulb at the bottom of the thermometer and, as temperature increases, the alcohol expands and rises through a glass capillary tube. The corresponding temperature is indicated by discrete degree markings along the glass tube. Early water-based thermometers were limited by the freezing point of water. Mercury thermometers can read from minus 38 to 350 degrees Celsius, but alcohol thermometers have an even lower freezing point and may read as low as minus 200 degrees Celsius.