Joseph Proust's law of definite composition says that pure chemicals are composed of elements in a definite formulation; we now know that the structural arrangement of these elements is also important.
Hukum perbandingan tetap dari Joseph Proust menyatakan bahwa zat kimia murni tersusun dari unsur-unsur dengan formula tertentu; kita sekarang mengetahui bahwa susunan struktural unsur-unsur ini juga penting.