The Collaborative International Dictionary of English v.0.48:

Polverine \Pol"ve*rine\, n. [It. polverino, fr. polvere ?ust, L.
   pulvis, -veris. See Powder.]
   Glassmaker's ashes; a kind of potash or pearlash, brought
   from the Levant and Syria, -- used in the manufacture of fine
   glass.
   [1913 Webster]