Mercury thermometer, Nairobi Industrial Area

A mercury thermometer is a precise temperature-measuring device consisting of a sealed glass tube filled with mercury, which expands and contracts in response to temperature changes. Known for its accuracy, this thermometer typically measures temperatures ranging from approximately -39°C (-38.8°F) to 356°C (672.8°F). The glass tube is calibrated with a scale marked in degrees Celsius or Fahrenheit, allowing for easy reading of the temperature via the distinct silver meniscus formed by the mercury. Although durable and resistant to certain chemicals, mercury thermometers pose environmental and health risks due to the toxic nature of mercury, leading many laboratories and institutions to transition to safer alternatives. Despite this shift, their reliable performance and consistent readings have made them a long-standing tool in scientific, medical, and industrial applications.