Encyclopedia > Triple point

  Article Content

Triple point

The triple point is the temperature and pressure at which three phases (gas, liquid, and solid) of a particular substance may coexist in thermodynamic equilibrium.

For water the triple point temperature is exactly 273.16 K (0.01 C) and the triple point pressure is 611.73 Pa (ca. 0.006 atm).

For mercury the triple point temperature is -38.8344 C. The triple point of water is used to define the Kelvin and the Celsius temperature scale; the number given for the temperature of the triple point of water is an exact definition rather than a measured quantity.

Note that the pressure referred to here is the vapor pressure of the substance, not the total pressure of the entire system.

See also Equations of State.

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article
Aurora australis

... on a patchy appearance and the patches often blink on and off once every 10 seconds or so until dawn. Most of the auroral features are greenish yellow but sometimes the tall ...