Looking at the appearance color of gold, as the saying goes, gold is "seven green, eight yellow, nine purple and ten red", showing different colors due to different types and components of impurities. Pure gold is shiny and shiny, and mixed gold is a bit rough. 70% jewelry with gold is yellow with blue, 80% jewelry with gold is yellow, 90% jewelry with gold is yellow with purple, 100% jewelry with gold is red.
In ancient times, people usually used the method of measuring density, that is, putting gold into water, measuring the volume, calculating the density according to the weight, and then comparing it with the known ones.
Experienced ancients will use the method of "weighing" to detect purity. The specific gravity of gold is 19.3g/cm3, and the fineness is closely related to the specific gravity. When the specific gravity is close to 19.3, the content of pure gold is higher. Weigh it by hand to see if it is commensurate with its size. Large and light shapes may be adulterated. But generally, if you hold it in your hand, you can feel that it is real gold jewelry when you feel a little heavier, indicating that the gold body is small and heavy.
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Some physical characteristics of gold:
The color of gold is golden yellow, which has a metallic texture and is not easy to decompose. Hardness 2-3, pure gold 19.3, melting point1064.4℃; Good ductility, can be pressed into thin foil, and has extremely high heat and thermal conductivity. The resistance of pure gold is 2.4p Pure gold has good chemical resistance and is the best electroplating material.
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.
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