Law of definite proportions was first given by Joseph Priestly. The law states that every chemical compound contains fixed and constant proportions (by mass) of its constituent elements, independent on the source and methods of preparation.
The law of definite proportions, also known as the law of constant proportions, states ‘that the individual elements that constitute a chemical compound are always present in a fixed ratio’ (in terms of their mass). This ratio does not depend on the source of the chemical compound or the method through which it was prepared.
The law of constant proportions explains that the chemical compounds are made up of elements that are present in a fixed ratio by mass and do not depend on their source and method of preparation. In any pure sample of a compound, the chemical compound will always comprise the same elements that are present in the same ratio by mass.
