According to the different luster and color of gold, pure gold, k gold, real gold and fake gold can be roughly distinguished. In other words, red and yellow (yellow-red) is the best gold with a fineness of over 95%; The fineness of positive yellow is about 80%; Cyan accounts for about 70%; Yellow is light gray, and the fineness is about 50%.

Therefore, there is a formula of "seven green, eight yellow, nine five red, yellow and white with gray and half gold". For a long time, there has been a saying that "copper turns green, silver turns black, and gold never changes color".

Step 2 consider

With the same volume of silver, lead and tin, the weight of gold is about twice. Real gold feels like falling in your hand, while copper or others only feel heavy and don't fall.

Step 3 use acid spots

The identified jewelry and reference gold were ground on the touchstone, and nitric acid was tested on the gold road with a glass rod. Because the chemical property of gold element is stable and does not react with acid, its color remains unchanged. If it is not gold or impure gold, the path of gold disappears or changes.

The law of change is "three fast and three slow", that is, the low color disappears quickly and the high color disappears slowly; Mixed gold disappears quickly, while clear gold disappears slowly; Large mixed gold disappears quickly, while small mixed gold disappears slowly. According to the disappearance of the golden path, the fineness of gold jewelry can be determined by comparison.

Burn with fire

Burn the jewelry to be identified (don't make it melt and deform), and observe the color change after cooling. If the surface is still golden, it is pure gold; If the color darkens or turns black to varying degrees, it is not pure gold. Generally, the lower the fineness, the thicker the color, and all of them turn black, indicating that they are fake gold ornaments. When it really burns red, it is quenched into water and its color remains unchanged. It really doesn't change color in case of fire, it doesn't resist fire, and it becomes dark purple.

Extended data:

As a precious metal, gold has good physical properties. "Real gold is not afraid of fire" means that gold has high chemical stability and is not easy to react with other substances, so there is no need to worry about oxidation and discoloration. Even in the molten state, it will not be oxidized and discolored, and it will still be golden yellow after cooling. High density and heavy touch.

Good toughness and ductility, good electrical conductivity. Pure gold is bright yellow, but the color changes greatly after mixing with other metals, such as gold-copper alloy is dark red, and silver-containing alloy is light yellow or grayish white. Gold is easily ground into powder, which is also the reason why gold is dispersed in nature. Pure gold jewelry is also easy to wear and lose weight.

In Mendeleev's periodic table, the atomic number of gold is 79, that is, the nucleus of gold contains 79 protons, which are positively charged. At the same time, gold has good chemical stability because it conforms to the half-full law. In the metal market, gold and ruthenium, rhodium, palladium, osmium, iridium, platinum and other metals are collectively called precious metals.

Although gold is a very soft metal, it is not as good as lead and tin. Nails can be used to draw marks on pure gold, which makes gold very easy to process. But this is not ideal for the manufacturers of decorations, because it is easy to scratch the decorations, make them lose their luster and even affect their appearance. Therefore, when gold is used to make jewelry, copper and silver are usually added to improve its hardness.