Safer Alternatives to Mercury Thermometers

Why is Mercury Thermometers classed as Dangerous Goods?

An article by Chester County, PA states that one gram of mercury can contaminate a 20-acre lake. Mercury coming out of a device or thermometer that is broken can contaminate surroundings and get inside the human body. Breathing it in is more dangerous than swallowing it. Mercury evaporates easily and can get in to your lungs, which is very poisonous and can lead to death.

Mercury is also considered a dangerous product to transport because it forms alloys with other metals very easily. When mercury comes into contact with aluminium it forms an amalgam and when that reacts with the air it causes the aluminium oxide to grow out and keep reacting continuously. Airplanes contain huge volumes of aluminium due to its durability, therefore, the reaction between aluminium and mercury can be a deadly combination. This let to any item that contains mercury, no matter how small, being classified as dangerous goods.

What is the most common alternate to Mercury Thermometers?

Mercury is the only metal that is a liquid at room temperature and has been the most preferred option in the past due to its excellent conductivity of heat and the fact that it does not wet the walls of the thermometer, which leads to greater accuracy in measuring temperature. However, the use of mercury has been deemed toxic and harmful, creating a supply gap due to the inablity to transport it. This led to the increase use of non-mercury alternatives.

The most common alternate to the mercury filling is alcohol. There are other organic, environmentally friendly and biodegradable options for thermometer filling in the market as well, but the alcohol thermometer is the most popular option as a general laboratory thermometer.

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Alcohol vs. Mercury

With limited access to mercury thermometers, it is useful to know the benefits and shortcomings of alcohol thermometers so you can identify the right thermometer for your application.

Advantages

• It is suitable to measure low temperatures because alcohol has a low freezing point.
• It is less toxic than mercury making it safe for humans and the environment.
• It has a higher coefficient of expansion than a mercury thermometer.
• It is less expensive than a mercury thermometer.

Disadvantages

• It is less durable because alcohol evaporates faster than mercury.
• It cannot measure high temperatures because of a low boiling point.
• It wets the walls of the thermometer, which can adversely impact the accuracy of readings.