why mercury cannot be used to measure very low temperature .Intead alchol is used since alchol is colourless .

Dear student ,
  • Freezing point of mercury is -38.8 degrees centigrade.
  • As the freezing point of mercury is -38.8 degrees centigrade, it is not possible to measure temperatures below this value.
  • So, the mercury thermometer is not preferred to measure low temperatures (below -38.8 degrees centigrade)
Alcohol thermometers may be used to measure temperatures from -115°C (freezing point of alcohol) to 785°C (boiling point of alcohol). The standard thermometer for environmental measurements need only cover the range -20°F to 120°F, or about -30°C to 50°C.
Alcohol can be used in some thermometers due the fact of its very low freezing point. It may be used in cold atmospheres such as freezers. It however would not be suitable in very hot atmospheres due to the boiling point.
 

Regards

  • 8
Ethanol-filled thermometers are used in preference to mercury for meteorological measurements of minimum temperatures and can be used down to −70 °C (-94 °F). The physical limitation of the ability of a thermometer to measure low temperature is the freezing point of the liquid used.
  • -2
Because mercury is a high level conductor
  • -8
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