In chemistry, the law of definite proportions, sometimes called Proust's Law or The Law of Definite Composition, states that a chemical compound always contains exactly the same proportion of elements by mass This observation was first made by the French chemist Joseph Proust, based on several experiments conducted between 1798 and 1804
In chemistry, the law of multiple proportions is one of the basic laws of stoichiometry used to establish the atomic theory, It is sometimes called Dalton's Law after its discoverer, the British chemist John Dalton,[1] [2] who published it in the first part of the first volume of his "New System of Chemical Philosophy" (1808)
The law of reciprocal proportions (also called the law of equivalent proportions[1] or law of permanent ratios[2] ) is one of the basic laws of stoichiometry. It relates the proportions in which elements combine across a number of different elements. It was first formulated by Jeremias Richter 1791.
The expression Gay-Lussac's law is used for each of the two relationships named after the French chemist Joseph Louis Gay-Lussac and which concern the properties of gases, though it is more usually applied to his law of combining volumes,