The Collaborative International Dictionary of English v.0.48:

Chemical \Chem"ic*al\, n.
   A substance used for producing a chemical effect; a reagent.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chemical \Chem"ic*al\, a.
   Pertaining to chemistry; characterized or produced by the
   forces and operations of chemistry; employed in the processes
   of chemistry; as, chemical changes; chemical combinations.
   [1913 Webster]

   Chemical attraction or Chemical affinity. See under
      Attraction.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chemical
    adj 1: relating to or used in chemistry; "chemical engineer";
           "chemical balance" [syn: chemical, chemic]
    2: of or made from or using substances produced by or used in
       reactions involving atomic or molecular changes; "chemical
       fertilizer"
    n 1: material produced by or used in a reaction involving
         changes in atoms or molecules [syn: chemical, chemical
         substance]

Moby Thesaurus II by Grady Ward, 1.0:

152 Moby Thesaurus words for "chemical":
   Chile saltpeter, absolute alcohol, acetate, acetone, acid, acidity,
   agent, alcohol, aldehyde, alkali, alkalinity, alloisomer, amine,
   ammonia, amyl alcohol, anhydride, anion, antacid, arsenate,
   arsenite, atom, base, basic, basic anhydride, benzoate,
   bicarbonate, bicarbonate of soda, bichloride of mercury,
   biochemical, bisulfate, borate, borax, bromide, calcium carbonate,
   calcium hydroxide, carbide, carbohydrate, carbon dioxide,
   carbon monoxide, carbonate, cation, chemical element, chemicals,
   chemicobiological, chemicoengineering, chemicomineralogical,
   chemicophysical, chemurgic, chlorate, chlorite, chromate,
   chromoisomer, citrate, compound, copolymer, copolymeric,
   copolymerous, copperas, cyanide, dehydrated alcohol, dichromate,
   dimer, dimeric, dimerous, dioxide, disulfide, electrochemical,
   element, elemental, elementary, ester, ethanol, ether, ethyl,
   ethyl alcohol, fluoride, formaldehyde, fulminate, halide, halogen,
   heavy chemicals, heteromerous, high polymer, homopolymer, hydracid,
   hydrate, hydride, hydrocarbon, hydroxide, hypochlorite,
   inorganic chemical, inorganic chemistry, iodide, ion, isomer,
   isomerous, isopropyl alcohol, ketone, lactate, macrochemical,
   macromolecule, metamer, metameric, methane, methanol, methyl,
   methyl alcohol, molecule, monomer, monomerous, monoxide,
   neutralizer, niter, nitrate, nitride, nitrite, nonacid,
   organic chemical, oxalate, oxide, oxyacid, permanganate, peroxide,
   petrochemical, phosphate, phosphide, photochemical,
   physicochemical, phytochemical, polymer, polymeric, potash,
   potassium nitrate, pseudoisomer, radical, radiochemical, reagent,
   sal ammoniac, salt, saltpeter, silicate, sodium bicarbonate,
   sodium bromide, sodium chloride, sodium hypochlorite, sulfacid,
   sulfate, sulfide, sulfite, tartrate, thermochemical, trimer