A Word to the Wise
litmus test
Chemically, the litmus (LIT-mus) test is used to determine whether a substance is acidic or alkaline. The test is performed by placing a small sample onto red or blue litmus paper. Red paper turns blue when the substance is alkaline; blue paper turns red when it is acidic. Because the results of the test are so definite and indisputable, the term is also applied to a single factor in any context that is considered to be crucial. As I used it today: “The OSS will turn you into a Stage One sales and marketing expert, becoming your secret litmus test to measure new ideas and make wise decisions.”