reagent

/ɹi.ˈeɪ.dʒɛnt/

IPA: /R IY0 EY1 JH AH0 N T/

noun
  1. 1

    A compound or mixture of compounds used to treat or test materials, samples, other compounds or reactants in a laboratory or sometimes an industrial setting.

Source: https://en.wiktionary.org/wiki/reagent