https://blog.gongquiz.com/2021/01/18/gibbs%ec%9d%98-%ec%83%81%eb%a5%a0phase-rule%ec%9d%84-%ec%98%ac%eb%b0%94%eb%a5%b4%ea%b2%8c-%ed%91%9c%ec%8b%9c%ed%95%9c-%ea%b2%83%ec%9d%80-%eb%8b%a8-p-%ec%83%81%e7%9b%b8%ec%9d%98-%ec%9d%91/