Azeotropy

...However, in certain solutions with a specific composition, the composition of the vapor becomes the same as the composition of the solution, and the vapor boils at a constant temperature (called the azeotropic point) without changing its composition, and behaves as if it were a pure liquid. This phenomenon is called azeotropy (from the Greek "does not change boiling point"), and the solution with that composition is called an azeotrope. In this case, azeotropy can occur at the lowest or highest boiling point of the system, the former is called the lowest (boiling point) azeotrope, and the latter is called the highest (boiling point) azeotrope. ...

*Some of the terminology explanations that mention "azeotropy" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…しかし，特定の組成をもったある種の溶液では蒸気の組成と溶液の組成とが同じになり，組成変化することなく一定温度(共沸点という)で沸騰し，あたかも純粋液体のごとく振る舞う。この現象を共沸azeotropy(ギリシア語の〈沸点を変えない〉に由来)と呼び，その組成の溶液を共沸混合物(アゼオトロープ)という。この際，共沸がその系の最も低い沸点で起こるか，最も高い沸点で起こるかの2通りの場合が存在し，前者は最低(沸点)共沸混合物，後者は最高(沸点)共沸混合物と呼ばれる。…

※「azeotropy」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報