subtilize

subtilize \SUHT-l-ahyz\, verb:

1. To make (the mind, senses, etc.) keen or discerning.
2. To elevate in character.
3. To make thin, rare, or more fluid or volatile; refine.

By long brooding over our recollections, we subtilize them into something akin to imaginary stuff, and hardly capable of being distinguished from it.
-- Nathanial Hawthorne, The Blithedale Romance

Another (ah Lord helpe) mee vilifies /With Art of Love, and how to subtilize, /Making lewd Venus, with eternall Lines, /To tye Adonis to her love's designes.
-- John Davies of Hereford, Papers Complaint, compil'd in ruthfull Rimes Against the Paper-spoylers of these Times

Subtilize grew in popularity among practitioners of alchemy and early medical theory.