Kopp's law can refer to either of two relationships discovered by the German chemist Hermann Franz Moritz Kopp (1817–1892).
- Kopp found "that the molecular heat capacity of a solid compound is the sum of the atomic heat capacities of the elements composing it; the elements having atomic heat capacities lower than those required by the Dulong–Petit law retain these lower values in their compounds."
- In studying organic compounds, Kopp found a regular relationship between boiling points and the number of CH2 groups present.
where N is the total number of compound constituents, and Ci and fi denote the specific heat and mass fraction of the i-th constituent. This law works surprisingly well at room-temperature conditions, but poorly at elevated temperatures.
- See page 96 of Millard, Earl Bowman (1921). Physical Chemistry for Colleges. New York: McGraw-Hill. p. 96.
- See page 942 of Miller, William Allen (1869). Elements of Chemistry. London: Longmans, Green, Reader, and Dyer.
- Kauwe, Steven K.; Graser, Jake; Vazquez, Antonio; Sparks, Taylor D. (2018-05-29). "Machine Learning Prediction of Heat Capacity for Solid Inorganics". Integrating Materials and Manufacturing Innovation. 7 (2): 43–51. doi:10.1007/s40192-018-0108-9. ISSN 2193-9764. S2CID 65239690.
- Thorpe, T. E. (1901). "The Life Work of Hermann Kopp". Memorial Lectures Delivered Before the Chemical Society. 25: 774–815.