acid test

A conclusive or critical test, as used to determine the worth, quality, or effectiveness of someone or something. The phrase comes from the 19th-century practice of testing metals in nitric acid to determine if they contained gold. Restructuring the organization will be the acid test that determines whether or not it can survive the sudden downturn in the economy. The first game of the season will be an acid test of the team's head new coach. The acid test for the new manager will come in the form of healthcare open enrollment. We really need it to go smoothly this year.

Fig. a test whose findings are beyond doubt or dispute. The senator doesn't look too popular just now, but the acid test will be if he gets reelected.

A decisive trial to determine worth or quality, as in Exposure to brilliant sunlight is the acid test for showing this fabric won't fade. Alluding to a 19th-century chemical test for distinguishing gold from other metals, this term was used figuratively by the early 1900s.

COMMON If you call something the acid test, it will prove how effective or useful something is. The acid test for the vaccine will be its performance in the south where the disease is more widespread. So far, I don't feel too bad but I'm waiting for my first really stressful day when things go wrong. That will be the real acid test. Note: Nitric acid can be used to test whether a metal is pure gold because it damages most metals but does not affect gold.

A conclusive trial to establish the truth or worth of something or someone. The term comes from a test long used to distinguish gold from copper or some other metal. Most corrosive acids do not affect gold, but a solution of nitric acid and hydrochloric acid dissolves the metal. Used literally by jewelers in the late nineteenth century, the term soon was employed figuratively, by U.S. president Woodrow Wilson among others.