A thermometer is an instrument that measures the temperature of a system in a quantitative way. In a mercury thermometer a glass capillary tube is filled with mercury and a standard temperature scale is marked on the capillary tube. With changes in temperature, the mercury expands and contracts in a consistent fashion and the temperature can be read from the scale.

Mercury thermometers can be used to determine body temperature, liquid temperature, and vapor temperature. There are two general types of mercury thermometers that measure body temperature (fever thermometers): 95 percent are oral/rectal/baby thermometers, and 5 percent are basal temperature thermometers. An oral/rectal/baby thermometer contains approximately 0.61 grams of mercury and a basal thermometer contains approximately 2.25 grams.

The temperature of liquids and vapors are often measured with mercury thermometers in households, in laboratory experiments at educational and medical institutions, and in industrial applications. Common household uses of mercury thermometers (other than fever thermometers) are oven, candy and meat thermometers. In educational and medical institutions, mercury thermometers may be used in many applications, including chemical experiments, water and acid baths, blood banks, ovens and incubators

Following are some common industrial applications where mercury thermometers may be found.

• Power plants and piping
• Chemical tanks and vats
• Heating and cooling equipment
• Engines, gasoline holding tanks
• Breweries, canneries, bakeries
• Candy making
• Dairies
• Ships
• Wineries and distilleries
• Paint and varnish kettles

A mercury thermometer can be easily identified by the presence of a silver bulb. (One exception to this is the new fever thermometers containing gallium, indium and tin that also contain a silver bulb but are clearly marked ?mercury-free.?) If the bulb is red, blue, purple, green or any other color, it is not a mercury thermometer.

Sources: U.S. EPA. Mercury Study Report to Congress Volume II: An Inventory of Anthropogenic Mercury Emissions in the United States. December 1997; http://www.palmerinstruments.com.