adulterant adulterant /əˈdʌltərənt/

adjective

1. Making impure or corrupt by adding extraneous materials  ( adulterant , adulterating )
   making impure or corrupt by adding extraneous materials
    The adulterating effect of extraneous materials
   the adulterating effect of extraneous materials
   

noun

1. Any substance that lessens the purity or effectiveness of a substance  ( adulterant , adulterator )
   any substance that lessens the purity or effectiveness of a substance
    It is necessary to remove the adulterants before use
   it is necessary to remove the adulterants before use