Acid test (gold) facts for kids

An acid test is a special kind of test, often using acid, to check if something is real or pure. It's most famous for telling the difference between real gold and other metals. The phrase "acid test" is also used to describe any very important or difficult test that shows the true quality of something, like a person's character or how well a product works.

How Do Chemists Use Acid Tests?

Testing for Gold Purity

Testing for gold with acid works because gold is a "noble metal". This means it doesn't easily change or get damaged by things like corrosion (rusting), oxidation (reacting with oxygen), or most acids.

To test for gold, you rub the gold-colored item on a special black stone. This leaves a small mark. Then, a chemist applies nitric acid to the mark. If the mark disappears, the item is not gold. Nitric acid dissolves most other metals, but not gold.

If the mark stays, it means it might be gold. The next step is to apply a stronger acid called aqua regia. Aqua regia is a mix of nitric acid and hydrochloric acid. If this acid removes the mark, it means the item is real gold. This is because aqua regia is one of the few acids that can dissolve gold.

Checking Gold's Fineness

Experts can even figure out how pure the gold is, which is called its fineness. They do this by using different strengths of aqua regia. They also compare the unknown item to pieces of gold with a known purity.

What Does "Acid Test" Mean Figuratively?

A Test of True Quality

The idea of an "acid test" as a way to check someone's character or the quality of materials became very popular. This happened especially during and after the California Gold Rush in the mid-1800s. People started using the phrase to mean a tough challenge that reveals the truth.

For example, a newspaper in 1845 wrote about someone's long service, saying it showed their ability "to stand the acid test." This meant they had proven their worth over many years.

Modern Examples of Acid Tests

Today, you can find the idea of an "acid test" in other areas too. For instance, there are special websites like Acid1, Acid2, and Acid3. These websites are designed to test how well web browsers follow the rules for building websites, called web standards. If a browser passes these "acid tests," it means it works correctly with most websites.

See also

In Spanish: Prueba ácida (oro) para niños