Gay-Lussac's law

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, the first listed here. The first law relates to volumes before and after a chemical reaction while the second concerns the pressure and temperature relationship for a sample of gas often known as Amontons' Law.