Litmus is a dye, first taken from certain mosses, that chemists use as a simple test. On paper it turns red when it touches acid and blue when it touches an alkali (a base — the opposite side from acid, like soap or baking soda). School science meets ‘litmus paper’ more often than the bare word.

Litmus is a dye,Litmus石蕊是一種染料 first taken from certain mosses,最早是從某些苔蘚裡取得的 that chemists use as a simple test.化學家拿它來做簡單的測試 On paper it turns red when it touches acid用在試紙上,碰到酸會變紅 and blue when it touches an alkali碰到鹼會變藍 (a base — the opposite side from acid, like soap or baking soda).(alkali也就是base,跟酸相反的那一邊,像肥皂或小蘇打) School science meets 'litmus paper' more often than the bare word.學校的科學課,比較常遇到'litmus paper石蕊試紙',而不是這個字單獨出現。

Though actually, in grown-up English the lab sense is not the one you hear most. People say a litmus test for a quick check that shows where someone really stands — a question or a moment that makes the truth show itself, the way the paper changes colour. That use is a picture borrowed from the lab, not a second chemical.

Though actually, in grown-up English the lab sense is not the one you hear most.不過,在大人的英文裡,實驗室的意思其實不是你最常聽到的那個 People say a litmus test人們會說a litmus test檢驗標準 for a quick check that shows where someone really stands —指的是一個能快速看出一個人真正立場的測試 a question or a moment that makes the truth show itself,一個問題,或一個時刻,能讓真相顯現出來 the way the paper changes colour.像試紙變色一樣 That use is a picture borrowed from the lab,這種用法是從實驗室借來的比喻 not a second chemical.不是第二種化學物質。

The colours themselves are worth keeping straight: red for acid, blue for alkali.

The colours themselves are worth keeping straight:顏色本身值得記清楚 red for acid,紅色代表酸 blue for alkali.藍色代表鹼。