Dispersive power

from The Collaborative International Dictionary of English v.0.48

Dispersive \Dis*pers"ive\, a.
   Tending to disperse.
   [1913 Webster]

   {Dispersive power} (Opt.), the relative effect of a material
      in separating the different rays of light by refraction,
      as when the substance is formed into a prism. --
      {Dis*pers"ive*ness}, n.
      [1913 Webster]