A lab thermometer mercury is a type of thermometer commonly used in laboratory settings for measuring temperatures. It consists of a glass tube with a bulb at one end and a scale marked on the tube. The bulb contains mercury, which expands and contracts with temperature changes, causing the mercury level to rise or fall in the tube.

The scale on the tube is marked in degrees Celsius or Fahrenheit, allowing the user to read the temperature. Mercury thermometers are accurate and reliable, but due to the toxicity of mercury, they are being phased out in favor of digital alternatives.