| Phase rule (phase rule) |
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| . (Phys. Chem.) ) |
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| Phase rule |
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A generalization
with regard to systems of chemical equilibrium, discovered by Prof. J.
Willard Gibbs. It may be stated thus: The degree of variableness
(number of degrees of freedom) of a system is equal to the number of
components minus the number of phases, plus two. Thus, if the
components be salt and water, and the phases salt, ice, saturated
solution, and vapor, the system is invariant, that is, there is only
one set of conditions under which these four phases can exist in
equilibrium. If only three phases be considered, the system is
univariant, that is, the fixing of one condition, as temperature,
determines the others.
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In celebration of Noah Webster's Birthday (October 16, 2009), we have prepared an updated website. 