Confirming whether or not gold is of an 21k quality is easy with this kit. To begin, just scrape off a piece of gold dust from an inconspicuous location of the jewelery. Use the included plastic wand to place a drop of this testing liquid on the gold dust. From there, just pay attention to the color change. If the color of the liquid remains consistent, the gold is 21k; if it changes, it's not 21k (lower in fact). Once complete, close the resealable container so it's ready for use in the future.
Warnig: Contains nitric acid (HNO3). Avoid contact with your hands. In the event of eye contact, rinse with plenty of water and seek medical attention. Keep out of the reach of children.