universal indicator
noun [ C ] chemistry specialized uk/ˌjuː.nɪ.vɜː.səl ˈɪn.dɪ.keɪ.tər/ us/ˌjuː.nɪ.vɝː.səl ˈɪn.dɪ.keɪ.t̬ɚ/
(化学上用的)通用指示剂(用来测定物质的酸碱性)
a chemical solution made from a mixture of substances that produce many different colour changes according to different pH levels, used to discover how acid or alkaline something is