phase rule

American  

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.

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phase rule British  

noun

1. 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

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phase rule Scientific  

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 state of matter

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Etymology

Origin of phase rule

First recorded in 1895–1900

Example Sentences

The question, moreover, has had a new light thrown upon it by the application of the principles of thermodynamics and of the phase rule.

From The New Physics and Its Evolution by Poincaré, Lucien