Other forms: litmus tests
In chemistry, a litmus test is used to find out if a solution is acidic or basic. During a litmus test, a strip of a special kind of colored paper is dipped into a liquid to see if it changes color.
A scientific litmus test is a fast and simple way to determine if a liquid is acidic or basic (also called alkaline). Acidic solutions turn blue litmus paper red, while alkaline solutions turn red litmus paper blue. A liquid with a neutral pH — neither acidic nor alkaline, such as water — will not affect the color of either type of litmus paper. The term litmus test is also used to talk figuratively about any simple, decisive test of something: "The vote was a litmus test of the voters' feelings about the economy."