Gold is a precious metal and one of the earliest metals discovered, developed and utilized by human beings. It is not only an important raw material for making jewelry and coins, but also an important reserve material for the country, and is known as the "king of metals". It is not only regarded as a symbol of beauty and wealth, but also benefits human life with its unique value. With the development of science and technology and modern industry, gold plays an increasingly important role in aerospace, medicine, electronics and other industrial fields. The use of gold is more and more extensive, and the consumption is also increasing, which has attracted special attention and strong interest from all countries in the world.
The atomic number of gold in the periodic table of chemical elements is 79, and the atomic weight is 197. Gold is heavy, but lighter than platinum. Is the density of gold19.32g/cm? That is, a golden ball with a diameter of only 46 mm weighs 1 kg. Pure gold is golden yellow, but it is rare in nature. The color of gold changes with the content of impurities: silver and platinum can lighten the color of gold; Copper will darken the color of gold. Colloidal gold shows different colors according to its dispersion degree and micro-adhesion structure.
Gold has good ductility. One or two pure gold can be hammered into gold leaves with a thickness of one tenth of a millimeter and an area of nine square meters. Gold leaves are transparent. When sunlight passes through them, they can be green. 50g of pure gold can spin 8km, which is thinner than hair (∮ 1.6, human hair 7). The volatility of gold is small, and the melting volatility can be ignored in general. The evaporation loss of gold in gas is 6 times that in air, and the loss of gold in carbon monoxide is 2 times that in air. The volatilization rate of gold is closely related to its impurity content.
Gold has good electrical and thermal conductivity. The thermal conductivity of gold is second only to silver and copper, ranking third among metals, and the thermal conductivity is 74% of that of silver. The chemical properties of gold are very stable. Gold will not be directly oxidized by oxygen at low temperature or high temperature. At room temperature, gold and single inorganic acids (such as hydrochloric acid, nitric acid and sulfuric acid) have no effect, but mixed acids, such as aqua regia (three parts hydrochloric acid and one part nitric acid) and cyanide solution can dissolve gold well. The melting point of gold is 1063℃. If gold is heated to near the melting point, it can be melted like iron, fine gold particles can be melted into blocks, and gold powder can only be fused together by pressing at low temperature. Gold can be alloyed with other metals, such as gold-silver alloy, gold-copper alloy and gold-silver-copper alloy. In addition, there are so-called gold amalgam.
Gold often exists in the state of natural gold. Natural gold containing silver and copper impurities is essentially different from the alloys of these metals. Alloy is the product of metal melting and solidification, so it has a homogeneous structure, while natural gold is precipitated from aqueous solution. Natural gold is sometimes covered with a thin film of iron oxide. In this case, the color of gold may be brown, dark brown or even yellow. This kind of gold generally has a coating, which is not only an oxide of iron, but sometimes it may be some fine gangue attached to the surface of gold particles. This inclusion not only affects the identification of gold, but also brings difficulties to mineral processing (mixed mercury or cyanidation).
platinum
Platinum is a white alloy, which is made by melting gold and other metals. Because platinum is scarce, expensive and has a high melting point, it is rarely used to produce true K platinum in general countries. At present, in order to meet the demand of consumers for platinum, gold, palladium or nickel, silver, copper, zinc and other metals are selected to be smelted into a white alloy, which is called "K platinum". The fineness of K-gold platinum is the same as that of K-gold, the bundle mass is 24, and the share of gold in it is the K number of "K-gold". For example, 18K platinum and 14K platinum have gold contents of 75% and 58.5% respectively.
Platinum, also called platinum. Its English name is Platinum, and it is generally coded by the abbreviation PT. Wg is the abbreviation of English White Gold, namely platinum.
The gold engraved with 14Kwg sold by merchants is 14K platinum, that is, the white alloy containing 25% palladium or nickel in gold is actually a kind of K gold, in which the mass fraction of gold is K number of "K Platinum" and the total mass is 24K. For example, the gold content of 18K platinum and 14 platinum is 75% and 58.3% respectively.
Gold (Au) is a yellow precious metal. Jewelry can be made of pure gold (that is, 24K or 999.9 gold) or alloys of different purity (also known as "K gold"). The most common are 18K gold (containing 75% pure gold) and 14K gold (containing 58.5% pure gold). Soft and malleable, can be refined into various shapes; However, because it is not easy to shape, most jewels inlaid with diamonds or precious stones must use alloys (also known as "K gold"). This alloy is harder than gold and can be used in various plastic designs. Moreover, the colors of K gold are various: gold, rose gold, green gold, platinum, blue gold and so on. The colors are really colorful! However, platinum is very popular in recent years; Gold, I have to find someone with a unique vision.