Le magasin sur strasbourg d'achat et vente or (Comptoir national de l'or Strasbourg)

Gold acid test kit to check gold purity.

ABOUT GOLD PURITY: As a measure of purity, one carat is 24 purities by mass. Therefore, we have X=24 Mg/Mm, where X is the carat rating of the material, Mg is the mass of pure gold in the material, and Mm is the total mass of the material. As such, 24-carat gold is 99.9% fine gold, 21-carat gold is .875 gold, 18-carat gold is 75% gold, 14-carat gold is .585% gold, 12-carat gold is 50% gold, 10-carat gold is .417% gold, 9-carat gold is .375% gold and 8-carat gold are .333% gold. If you are up to it, you can determine the purity of your gold at home by using a popular method of relative accuracy.


This test requires a set of testing needles with different tips of exact karat, a testing stone and some acids. The testing solutions are meant to be used on finished jewelry because there are general guidelines about 10, 14 18k alloys and such. With a nugget, the content could be anything. That being said, the testing solutions will work the same way. They don’t dissolve the gold, but the alloy metals mixed with the gold. The gold will flake off, but won’t dissolve. So, the more gold, the more prominent the mark will remain. Low karat marks have little gold and will dissolve away, but high karat marks will remain “brighter” if I can use that word. the acid test kit, the acidic solutions contain nitric acid & hydrochloric acid. Base metal alloys will be dissolved by the acid whereas real gold will survive the corrosive acid test.

Pre-mixed acids come in easy-to-use plastic bottles that are entirely secure, and come with color-coded caps.  You can use these acid tests on jewelry that has been properly filed to reveal the base metal (if any). The pre-mixed acids can be used for 10K, 14K, 18K and 22K gold.

Rub a small piece of your item on the test stone and leave a visible deposit.  Select the needle that is the nearest to the karat value you believe the gold to be and rub it on the test stone, leaving a visible mark next to your first deposit.  Leave a drop of the acid approximating the karat that you believe your item to be.

GOLD TESTING Question & Answer.

  • You have tested my gold. One batch dont not even dissolve under 22k solution. If you still have a strong gold mark left behind after using the 22k solution, them that is a good sign that’s your gold is pure, at 24k, which one don’t contain alloy metal. 
  • How to check if my gold coin is real without scratching it or pouring acid on it? Weigh it and measure the height and diameter and compare that against the official specs. You can also use an XRF spectrometer.
  • How do you acid test a jewel without scratching it? : You have to scratch the jewel on the stone. If you don’t want to scratch it, you can use an XRF spectrometer.
  • There is no certain amount of time that have to passes for the line to disappear. the acid is simply strong enough to eat away at it at all.
  • What happen with something gold plated with either 14 or 18 karat gold? You should file it down a bit to be sure you don’t test the gold plating. Things are also only really gold plated with 24k gold. They can’t really gold plate with 18 karat gold or lower purities.
  • I store my acid kit in a sealed jar in a cool place away from the window and any light source; but how can I smell the vapors from the acid in the jar? They are all sealed tight. Acids are corrosive and even when sealed in their original factory the top dispenser can leak. Placing them closed and sealed into an air tight container will limit their exposure to their immediate environment but nor prevent 100% transfer. I suggest always wearing disposable latex gloves, a mask and keeping arm’s length distance from applying acids to testing stones. Flushing residential acids from testing stones with tap water and disposing of disposable towels into a sealed bag in the trash afterwards to prevent additional fumes.
  • Why two marks react the same way to the acid: then you will know that the gold content (karat value/purity) of your test sample is the same as that of the needle.
  • Why my test sample mark reacts sooner than your needle mark: your test sample has a lower gold content. When your needle mark reacts sooner than your test sample mark, your test sample has a higher karat value.  You can repeat these trials until you are able to find a close approximation of the karat of the gold item being examined.
  • My gold sample has no reaction to the acid: this will reveal that your sample is of higher karat than the acid. In this case you can test again, using a higher test needle and acid until there is a reaction. This way the karat of the gold item can be determined to a closer approximation.





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