Nitric Acid is then applied to the mark. If it easily dissolves, the item is not Gold. If the mark remains, Aqua Regia (Nitric Acid and Hydrochloric Acid) is then applied. If mark is removed then this test proves the gold is genuine.
The acid test for gold is to rub the gold-colored item on black stone, which will leave an easily visible mark. The mark is tested by applying nitric acid, which dissolves the mark of any item that is not gold, stainless steel, zinc, tungsten, aluminum, platinum, or palladium.
For gold, acids are designed to test to the nearest carat commonly used in jewellery, 9ct, 14ct 18ct, 22ct – but, with practice, results to within 5% can be achieved, very accurate!
Genuine gold will stand up to your attempt to conduct a nitric acid test at home. Make a tiny mark on the piece of gold to penetrate the surface. Drop a small amount of liquid nitric acid on that scratch and wait for a chemical reaction. Fake gold will immediately turn green where the acid is.
A mix of 3:1 of nitric and hydrochloric acids (also known as the aqua regia) is the only acid mixture that can dissolve gold, even the purest one. You can use this solution only if your gold successfully passed all the nitric acid tests.
Test With Nitric Acid
Make a mark deep enough to scratch through the top layer of gold. Carefully apply a drop of nitric acid to the mark, and determine if the mark turns green or milky. There will be no reaction if the jewelry is either gold or mostly gold.
If it easily dissolves, the item is not Gold. If the mark remains, Aqua Regia (Nitric Acid and Hydrochloric Acid) is then applied. If mark is removed then this test proves the gold is genuine.
The apple cider vinegar gold test is a great choice if you want to test your jewelry at home, as it is readily available and easy to do. After all, real gold will not react when exposed to the acids in vinegar, toothpaste and more.
Lower-karat gold pieces may produce a mild cupric reaction, which includes minimal to no fumes, no color change, and little to no bubbling. You may see a small black mark where the acid came into contact with the piece.
Nitric acid can help determine the presence of base metals in gold items. Apply a small amount of nitric acid to a discreet part of the item. Observe any color changes; if the acid causes the metal to turn green, it may indicate a lower gold content.
How to Test Gold With Vinegar. Apply a few drops of white vinegar to your gold jewelry. Real gold will not change color, but vinegar can cause fake gold items to react and change color.
The traditional acid test for gold consists of placing a small drop of a strong acid, such as nitric acid, onto the metal's surface. Most metals fizz and bubble, while precious metals remain unaffected.
Vinegar Test
Once you have some vinegar, clean your piece of jewelry with a rag or cloth to remove any dirt so you don't get faulty results. Then, place your jewelry into a bowl and add a few drops of your vinegar into the bowl. Real gold will not change color, but fake gold will turn either black or green.
Silverand gold does not react with HCl. This is because, like other reactive metals, they cannot displace hydrogen from HCl.
Make a small scratch on the gold and add a drop of bleach. If it changes color, your jewelry is not 100% pure 24K gold. Bleach can permanently damage gold jewelry. It can't tell you if your gold is fake, since most gold jewelry has other metals mixed in to give it strength.
Another source of acid can be found in your local auto parts store under the name “battery acid.” Battery acid is a dilute form of sulfuric acid, but any of them will work for this test. If the material forms than crystals, and it is the color of gold is most probably fools gold.
Testing Gold with Vinegar
One way you could test the purity of gold is by using vinegar. All you need to do is get the jewelry item you want to test and white vinegar. If the metal of the jewelry changes its color, it is not pure gold and if it keeps shining then you have real gold in your hand.
For this simple test, all you'll need are a few drops of vinegar. Find an inconspicuous location on your gold jewelry item and apply a bit of vinegar to the metal. Real gold won't change color but if the metal is fake gold, there may be a change.
The Ceramic Scratch Test
Take an unglazed ceramic plate or piece of tile and scrape a piece of gold across its surface. Real gold will leave a gold mark or trail. Other metals will leave a black trail.