Law of definite proportions
Ley de las proporciones definidas
- Date
- 1797 · confidence medium
- Place
- Segovia and Madrid, Spain
- Credited to
- Joseph-Louis Proust
- People
- 👤 Louis Proust1754–1826
- Field
- Matter & energy
⚠️ Disputed: the sources disagree.
What was discovered
A chemical compound always contains the same elements in the same mass proportions, regardless of its origin. It distinguishes a compound from a mixture and underpins atomic theory.
A long dispute with Berthollet, who argued for variable compositions (today's non-stoichiometric compounds, or berthollides).
What it led to
- Dalton's atomic theory
- Stoichiometry
- Concept of a pure compound
Built on
- Law of conservation of mass1789
- gravimetric analysis
Made possible
- Dalton's atomic theory and law of multiple proportions1803-1808
- quantitative mineral analysis