# Caput mortuum

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For the pigment, see [Caput mortuum (pigment)](/source/Caput_mortuum_(pigment)).

***Caput mortuum*** (plural *capita mortua*; literally "dead head") is a [Latin term](/source/Latin_term) used in [alchemy](/source/Alchemy) to signify a useless substance left over from a chemical operation such as [sublimation](/source/Sublimation_(chemistry)) and the epitome of decline and decay (alternatively called *[nigredo](/source/Nigredo)*). Alchemists represented this residue with a stylized human skull, a literal [death's head](/source/Human_skull_symbolism).[1][2]

The symbol shown on this page was also used in 18th-century chemistry to mean *residue*, *remainder*, or *residuum*. *Caput mortuum* was also sometimes used to mean *crocus metallorum*, i.e. brownish-red metallic compounds such as *crocus martis* ([ferrous sulfate](/source/Ferrous_sulfate)), and *crocus veneris* ([copper oxidule](/source/Copper_oxidule)).[3]

## References

1. Eastaugh, Nicholas (2004). [*Pigment Compendium: A Dictionary of Historical Pigments*](https://archive.org/details/pigmentcompendiu00east_788). [Butterworth-Heinemann](/source/Butterworth-Heinemann). p. [81](https://archive.org/details/pigmentcompendiu00east_788/page/n93). ISBN 0-7506-5749-9.

1. [https://web.archive.org/web/20100909043853/http://www.chemheritage.org/community/periodic-tabloid/2010-08-31-pounds-ampersands-and-skulls.aspx](https://web.archive.org/web/20100909043853/http://www.chemheritage.org/community/periodic-tabloid/2010-08-31-pounds-ampersands-and-skulls.aspx)

1. Liungman, Carl G. (2004). [*Symbols: Encyclopedia of Western Signs and Ideograms*](https://books.google.com/books?id=06ALKxX225IC). Ionfox AB. p. 236. ISBN 91-972705-0-4. Retrieved 2023-01-20. – via [Google Books](/source/Google_Books)

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Adapted from the Wikipedia article [Caput mortuum](https://en.wikipedia.org/wiki/Caput_mortuum) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Caput_mortuum?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.