The temperature at which liquid and solid water are in equilibrium under atmospheric pressure. The ice point is by far the most important “fixed point” for defining temperature scales and for calibrating thermometers. It is 273.15 K (0°C or 32°F). A closely related point is the triple point, where liquid, solid, and gaseous water are in equilibrium. It is 0.01 K (0.018°F) higher on the Kelvin scale than the ice point. The triple point has gained favor as the primary standard since it can be attained with great accuracy in a simple closed vessel, isolated from the atmosphere. Readings are reproducible to about 0.0001 K (0.0002°F), but dissolved gases or other foreign matter may raise the error to 0.001 K (0.002°F) or more.