21.2. Temperature Scales
To measure and compare temperatures, it is necessary to have agreed scales of temperature. These temperature scales are defined in terms of physical phenomena that occur at constant temperatures. The temperatures of these phenomena are known as
21.2.1. Celsius Temperature Scale
The Celsius temperature scale is defined by international agreement in terms of two fixed points: the ice point and the steam point. The temperature of the
ice point is defined as 0° Celsius and the
steam point as 100° Celsius.
The ice point is the temperature at which ice and water exist together at a pressure of 1.0132 × 10
−2 (originally one standard atmosphere = 760 mm of mercury). The ice should be prepared from distilled ...