law of definite proportion

law of definite proportion

[′lȯ əv ¦def·ə·nət prə′pȯr·shən]
(chemistry)
The law that a given chemical compound always contains the same elements in the same fixed proportion by weight. Also known as law of definite composition.
References in periodicals archive ?
Without the atomic hypothesis the law of the additivity of masses and the law of definite proportions remain entirely independent of one another.
In 1789 Antoine Lavoisier formulated the law of conservation of mass, and in 1799 Joseph-Louis Proust stated the law of definite proportions, allowing chemists to distinguish between mixtures and compounds.
He went on to make a similar case for a number of other compounds and maintained that there was a general law of definite proportions, often called Proust's law.