Mercury fever thermometers are composed of straw-sized glass and contain a silvery-white liquid within. They are widely used in many homes, schools, and medical establishments. The color of the liquid within the thermometer affects how it is calibrated. If the liquid is red, then it means that the temperature reading on the thermometer is incorrect. However, if the liquid is blue, that means that the thermometer is accurate to 1/4 degree F.
In addition to being inaccurate, thermometers with red liquids are dangerous because they cannot be trusted to show correct temperatures over time. Mercury has natural tendencies to want to spread out until it gets into something soft, like blood or an ink line. This can lead to inaccurate readings over time.
The chemical compound used to make the liquid inside thermometers is called quicksilver. It is made up of elemental mercury (Hg) combined with other elements such as arsenic (As), cadmium (Cd), or zinc (Zn). These other elements are added to improve the quality of the quicksilver and allow it to do its job better. For example, arsenic helps the quicksilver resist breaking down even at high temperatures, while cadmium makes the liquid clear. Without these additives, thermometers would break down too quickly to be useful.
Mercury Thermometers contain mercury. Before 1970, all thermometers did. Since then, most have been replaced with thermocouples or thermal sensors. Still used in veterinary medicine because they are easy to read even under black-out conditions.
The mercury in a thermometer works by expansion: As the mercury gets hot it expands, which moves a pointer on the side of the glass tube. Before 1970, all thermometers showed temperature as high or low readings based on the size of a pellet of mercury. The larger the pellet, the higher the reading. Smaller pellets indicated lower temperatures.
People who work with mercury should take special precautions to avoid exposure to this chemical. It is poisonous if ingested or absorbed through the skin. If you come into contact with mercury, remove any surface dust using a clean, dry towel or sponge. Put anything containing mercury into a safe container for disposal. Check with your local government agency about how to dispose of hazardous materials.
Modern thermometers usually contain silicon chips instead of mercury. These thermistors change shape when exposed to heat, which changes their electrical resistance. This information is translated into digital numbers by computers today.
Assume the thermometer contains mercury if it includes silver liquid and is not labeled "mercury-free." Colored alcohol is commonly used in non-silver liquid-in-glass thermometers. In some cases, mercury can be harmful. The majority of oral and rectal thermometers contain 0.5-0.6 grams of mercury. Oral thermometers are usually made of plastic and do not contain any silver. Rectal thermometers may use a mixture of plastic and silver.
The American Society for Testing and Materials (ASTM) has approved electronic thermometers for use on animals. These thermometers do not contain mercury. Electronic thermometers that measure body temperature by infrared radiation or digital technology are available commercially.
In addition to being hazardous if ingested by children or pets, mercury also poses a risk when it is released into the environment. For this reason, many health organizations do not recommend using mercury thermometers. Instead, they recommend electronic thermometers, which are a safe alternative.
In conclusion, yes, glass thermometers still have mercury in them. They should not be used because they pose a hazard to children and others who might be able to get their hands on them. Electronic thermometers are your best option if you want to avoid exposing yourself to mercury.