🝎

A simplified skull. Variants may look like ⟨💀︎⟩.

🝎

1. (alchemy, archaic) caput mortuum
2. (alchemy, archaic) nigredo

🝎o f (genitive 🝎is); third declension

1. (alchemy) abbreviation of nigredo
   • c. 1653–1656, George Starkey, translated by William R. Newman, Lawrence M. Principe, Alchemical Laboratory Notebooks and Correspondence, University of Chicago Press, published 2004, pages 188, 196:

     Accepi 🜰li 1ae fus: ℥46, 🝎i 🜅is ℥57, in ollâ amplâ simul liquavi, & ◻is Marini lb Circiter 3 addidi.
     tum 🝭am frange, & sublimatum separa a 🝎o, quod etiam aquâ calidâ Elixa, puta salem dulcem 🜖atum purum in se Continet quem extrahe.

     I took 46 oz of regulus of the first fusion and 57 oz of nigredo of aquafort, and I melted them together in a large pot and added about three pounds of sea salt.
     then break your retort and separate the sublimate from the nigredo, which you should also wash with hot water, to extractthe sweet vitriolate salt that it contains within itself.

Third-declension noun.