Noun
(chemistry) law stating that every pure substance always contains the same elements combined in the same proportions by weight
Source: WordNetBut it was found later that Berthollet was not completely wrong because there exists a class of compounds that do not obey the law of definite proportions. Source: Internet
Non-stoichiometric compounds main Although very useful in the foundation of modern chemistry, the law of definite proportions is not universally true. Source: Internet
The law of definite proportions might seem obvious to the modern chemist, inherent in the very definition of a chemical compound. Source: Internet