The Collaborative International Dictionary of English v.0.48:

Neutralizer \Neu"tral*i`zer\, n.
   One who, or that which, neutralizes; that which destroys,
   disguises, or renders inert the peculiar properties of a
   body.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "neutralizer":
   acid, acidity, agent, alkali, alkalinity, alloisomer, anion,
   antacid, antidote, atom, base, biochemical, buffer, cation,
   chemical, chemical element, chromoisomer, compound, copolymer,
   counteractant, counteractive, counteragent, counterirritant, dimer,
   element, heavy chemicals, high polymer, homopolymer, hydracid,
   inorganic chemical, ion, isomer, macromolecule, metamer, molecule,
   monomer, nonacid, nullifier, offset, organic chemical, oxyacid,
   polymer, preventative, preventive, prophylactic, pseudoisomer,
   radical, reagent, remedy, sulfacid, trimer