menstruum

/ˈmɛn.stɹʊəm/

Etymology

From Latin mēnstruum (“menstrual discharge”).

noun

The menses; menstrual discharge.
A solvent.“Whenever any menstruum or other additament is employed, together with the fire, to obtain a sulphur or a salt from a body, we may well take the freedom to examine, whether or no the menstruum do barely help to separate the principle obtained by it...”
Any liquid medium