26 Sep

Thermometers

Alcohol thermometers or spirit filled thermometers are rapidly replacing mercury thermometers in the laboratory.  Concern for mercury spills due to breakage has decreased the use of mercury thermometers.  The floors of older laboratories which use thermometers routinely probably have a large amount of  mercury contamination.  Many states do not allow shipment of mercury or mercury containing products including thermometers.

The melting point of mercury is around -40 deg C and -40 Deg F; spirit thermometers are necessary for measuring lower temperatures.  The boiling point of Ethanol is 78 deg C so other organic liquids are used in spirit thermometers for measuring higher temperatures.  Unfortunately the standard spirit filled or alcohol thermometers are not considered as accurate as a mercury thermometer.  This is changing and the manufacturers of spirit thermometers are now producing ASTM grade thermometers as accurate as mercury thermometers.  Spirit filled NIST calibrated thermometers are also available as standards for checking the accuracy of routine thermometers.

Another alternative to the Hg thermometer is electronic thermometers based on the response of a thermocouple.  These thermometers are available with certificates of accuracy from NIST certified laboratories.  Soon there will be very little reason to use mercury thermometers in the laboratory.

Robin Prymula