Feature 1This kit is used to verify the gold content in items 2This product set is only suitable for gold. 3Acid changes color based on purity. 4Very easy to use. Just apply a drop of this solution to a small sample of the item to be tested. 5The product set consists of high purity graphite stone and acid test waterSpecificationFeatures: This kit is used to verify the gold content in items This product set is only suitable for gold. Acid changes color based on purity. Very easy to use. Just apply a drop of this solution to a small sample of the item to be testedThe product set consists of high purity graphite stone and acid test water Specification: Material: High purity Graphite Stone and Acid Testing Water Graphite Stone Size: Approx. 4.1 x 1.1 x 7.2cm or 1.61 x 0.43 x 2.83inch Acid Testing Water Size: Approx. 3 x 1.2 x 4.7cm or 1.18 x 0.47 x 1.85inch Total Weight: 90g Type: Jewelry Tools and Equipments Package List: 1 x Graphite Stone 3ml x Acid Testing Water Note: How to use: If you want test your gold ring is real or not, just need rub black stone, and leave a small sample on stone Apply a drop of this solution to a small sample of the item to be tested onto the test stone. Then the real gold will stay on the touchstone, false one will be dissolved or oxidized to blue If the sample disappears, then the item is below the karat of the solution. .wang-edit-text{ font-family:'Arial' important } .wang-edit-text table { border-top: 1px solid 000 border-left: 1px solid 000 } .wang-edit-text table td, .wang-edit-text table th { border-bottom: 1px solid 000 border-right: 1px solid 000 padding: 3px 5px } .wang-edit-text table th { text-align: center } Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.