Dulong and Petit's law

noun

Du·​long and Pe·​tit's law ˈd(y)ü-ˌlȯŋ-ən-pə-ˈtēz-, d(y)ü-ˈ 

: a law in physics and chemistry: the specific heats of most solid elements multiplied by their atomic weights are nearly the same averaging a little over six calories per degree Celsius per gram-atomic weight