the acid test

acid test

A conclusive test. 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.
See also: acid, test

the acid test

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.
See also: acid, test

the acid test

a situation or event which finally proves whether something is good or bad, true or false, etc.
The original use of the phrase was to describe a method of testing for gold with nitric acid (gold being resistant to the effects of nitric acid).
1990 Which? These deals are designed to encourage impulse buying, so the acid test is whether you would have bought anyway.
See also: acid, test

the ˌacid ˈtest (of something)

(also the ˈlitmus test especially in American English ) a situation which finally proves whether something is good or bad, true or false, etc: They’ve always been good friends, but the acid test will come when they have to share a flat.Both these expressions originally referred to chemical tests. The acid test uses nitric acid to test if something is made of gold. The litmus test uses litmus paper to test for acids and alkalis.
See also: acid, test