are arbitrary thermometric calibrations that serve as
convenient references for temperature determination. There are two widely
used thermometric scales based on the freezing and boiling point of water at
a pressure of one atmosphere:
Fahrenheit (F) scale (32° = freezing, 212° =
boiling);
Celsius (C), or Centigrade, scale (0° =
freezing, 100° = boiling);
Additionally, there are two scales in which 0° = absolute
zero, the temperature at which all molecular movement theoretically ceases:
Kelvin (K), or Absolute (°A), scale;
Rankine (°R) scale, which are related to the
Celsius and the Fahrenheit scales, respectively (0°K = -273.16°C; 0°R =
-459.69°F). The four scales can be related to each other by the following
formulas:
°C = 5/9 (°F-32)
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°F = 9/5 °C+32
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°K = °C + 273.16
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°R = °F + 459.69
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Another scale based on the thermometric properties of
water is the Reaumur scale, in which the freezing point is set at
zero degrees and the boiling point at 80 degrees. This scale has only
limited application