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Features of a Mercury Thermometer

The mercury-in-glass thermometer was first invented by Daniel Fahrenheit, a scientist and a glassblower, in 1714. In addition to creating his own mercury thermometer, Fahrenheit also invented his own standardized temperature reading scale, which, combined with thinly blown glass tubes, had more scale degrees, hence more accuracy, than the Celsius scale.

  1. Maximum Thermometer Design

    • The glass in the mercury thermometer narrowed once it reached the point on the scale where the mercury registered a temperature. Since the glass is more constricted directly over the mercury housing bulb, extra force and pressure from quickly shaking the instrument must be used to allow the mercury to return to the bulb, thus resetting the thermometer. Known as maximum thermometers, these types of mercury thermometers were used in the medical field because the observing health care professional or parent could read the maximum temperature of the patient without hovering over the patient.

    Mercury

    • Mercury was used in the mercury thermometer due to its ability to remain at a constant density, unlike water, which expands during the freezing process. Many models of the mercury thermometer also used a bulb placed at the end of the thermometer, which housed most of the liquid mercury. The bulb helped increase the sensitivity and accuracy of the thermometer.

    Fahrenheit - Celsius

    • Most mercury-in-glass thermometers also used both Fahrenheit and Celsius scales, which were marked on either side of the mercury tube. Due to the accuracy of the Fahrenheit scale, most medical professionals in the US utilize the scale when treating patients. Mercury thermometers may be used for other purposes besides determining body temperature, which may result in the need for the use of the Celsius scale.

    Hazards

    • Since the early 2000s, mercury medical thermometers have been phased out due to the dangers of broken glass and inhaling fumes from the mercury, which could lead to potential health problems. According to Harvard University, it costs over $100 to clean up each mercury spill due to the environmental hazards and water pollution control measures that must be taken when a thermometer breaks. Tips for mercury spills include isolating the area, wearing protective gloves and safety glasses and using a leak-proof plastic container to contain the spill and broken glass.

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