在一个N个组元、Φ个相组成的平衡体系中,若参变量仅有温度T、压强P和浓度x_i~φ,x_i~φ表示第i个组元在第φ个相中的摩尔分数,i=1,2,……,N;φ=1,2,……,φ。根据相律,平衡体系中的自由度f由下式决定: f=C-Φ+2 (1)C为体系中的独立组元数。它的定义是若用最少数的独立变动的组元能把平衡体系中各相的 In an equilibrium system consisting of N components and Φ phases, if the parameter has only temperature T, pressure P, and concentration x_i~φ, x_i~φ represents the mole fraction of the ith component in the φth phase. i=1,2,...,N;φ=1,2,...,φ. According to the phase law, the degree of freedom f in the equilibrium system is determined by the following formula: f=C-Φ+2 (1) C is the number of independent components in the system. Its definition is to balance the phases of the system with the fewest independently changing components.