phase rule

noun

, Physical Chemistry.

1. a law that the number of degrees of freedom in a system in equilibrium is equal to two plus the number of components less the number of phases. Thus, a system of ice, melted ice, and water vapor, being one component and three phases, has no degrees of freedom. Compare variance ( def 4 ).

phase rule

noun

1. See component, degree of freedom
   the principle that in any system in equilibrium the number of degrees of freedom is equal to the number of components less the number of phases plus two See also degree of freedom component

phase rule

1. A rule used in thermodynamics stating that the number of degrees of freedom in a physical system at equilibrium is equal to the number of chemical components in the system minus the number of phases plus the constant 2.
2. Also called Gibbs phase rule
3. See also phase transition

Word History and Origins

Origin of phase rule¹

First recorded in 1895–1900

Example Sentences

To these questions an answer can also be given with the help of the Phase Rule.

From Project Gutenberg

As we shall learn, the Phase Rule enables us to give an answer to this question.

From Project Gutenberg

The relations between the various systems, however, become perfectly clear and intelligible in the light of the Phase Rule.

From Project Gutenberg

For other examples of the application of the Phase Rule to isomeric substances, see Journ.

From Project Gutenberg