universal indicator
noun/ˌjuːnɪˌvɜːsl ˈɪndɪkeɪtə(r)/
/ˌjuːnɪˌvɜːrsl ˈɪndɪkeɪtər/
(chemistry)- a substance that changes colour when another substance touches it, indicating whether it is an acid or an alkali
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universal indicator