The Collaborative International Dictionary of English v.0.48:

Essentiate \Es*sen"ti*ate\, v. t. [imp. & p. p. Essentiated;
   p. pr. & vb. n. Essentiating.]
   To form or constitute the essence or being of. [Obs.]
   --Boyle.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Essentiate \Es*sen"ti*ate\, v. i.
   To become assimilated; to be changed into the essence. [Obs.]
   --B. Jonson. Essoin