litmus

/ˈlɪtməs/ (bre, ipa) · /ˈlɪtməs/ (ame, ipa) · /ˈlit-məs/ (ame, mw)

litmus — noun

1. A natural substance obtained from lichens that reveals whether a liquid is an ac

1.名詞B2
釋義

A natural substance obtained from lichens that reveals whether a liquid is an acid or an alkali by changing colour — it turns red in the presence of an acid and blue in the presence of an alkali. It is most often used in the form of litmus paper.

例句

Mei dipped a strip of litmus paper into the beaker and watched it turn blue.

litmus paper: the common practical form

The chemistry teacher showed the class how litmus changes colour when it touches lemon juice.

同義詞
  • indicator

    a broader term for any substance that shows chemical conditions through a colour change

  • reagent

    a general term for any substance used in a chemical reaction to detect or measure another substance

用法筆記

Commonly appears as 'litmus paper' (the practical form used in labs) and figuratively in the fixed phrase 'litmus test' (a decisive test that reveals a person's true character or the true nature of a situation).

常見錯誤

❌Litmus are used in chemistry experiments.
✅Litmus is used in chemistry experiments.
💡litmus is an uncountable noun and always takes a singular verb.
❌I tested the water with a litmus.
✅I tested the water with litmus paper.
💡in practical contexts, 'litmus paper' is the natural term, not 'litmus' alone.