whitener

from WordNet (r) 3.0 (2006)

whitener
    n 1: an agent that makes things white or colorless [syn:
         {bleaching agent}, {bleach}, {blanching agent}, {whitener}]

from The Collaborative International Dictionary of English v.0.48

Whitener \Whit"en*er\, n.
   1. One who, or that which, whitens; a bleaching agent; a
      bleach; a bleacher; a blancher; a whitewasher.
      [1913 Webster]

   2. A chemical used as an adjunct to laundering white cloth,
      which makes white cloth appear whiter. A bluing agent.
      [PJC]