Gold and platinum
Gold Gold is a precious metal, one of the earliest metals discovered and exploited by mankind. It is an important raw material for making jewelry and coins, as well as an important reserve material of the country, and is known as the king of metals. It is not only regarded as a symbol of beauty and wealth, but also known for its gold. Gold is a precious metal and one of the earliest metals discovered and developed by mankind. It is an important raw material for making jewelry and coins, as well as an important reserve material of 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 is increasingly playing an important role in astronautics, medicine, electronics and other industrial sectors. Gold is used more and more widely, and its consumption is also increasing, which has aroused special concern and keen interest in gold from all countries in the world. The atomic number of gold in the periodic table of chemical elements is 79 and its atomic weight is 197. Gold is heavy, but lighter than platinum. The density of gold is 19.32 g/cm', that is, a gold ball with a diameter of only 46 mm has a weight of 1 kg. Pure gold is golden yellow, but in nature, pure gold is extremely rare. The color of gold changes with the content of impurities: silver and platinum can make the color of gold lighter; copper can make the color of gold darker. Colloidal gold shows different colors according to its degree of dispersion and micro-adhesive structure. Gold has good ductility. One or two pure gold can be hammered into a gold leaf that is one ten thousandth of a millimeter thick, which can cover an area of u200bu200bnine square meters. The gold leaf is transparent, and when sunlight passes through, it can appear green. 50 grams of pure gold can be threaded for 8,000 meters, which is thinner than hair (∮1.6, 7 for human hair). The volatility of gold is small. Under normal circumstances, the volatilization amount of gold is negligible. The amount of gold lost by evaporation in gas is six times that in the air. The loss of gold in carbon monoxide is twice that in the air, and the volatilization rate of gold is less than that in the air. The impurity content has a lot to do with it. Gold has good electrical and thermal conductivity properties. The electrical conductivity of gold is second only to silver and copper, and ranks third among metals, with a thermal conductivity of 74% of silver. The chemical properties of gold are very stable. Gold will not be directly oxidized by oxygen at low or high temperatures. At room temperature, gold and separate inorganic acids (such as hydrochloric acid, nitric acid, and sulfuric acid) do not work, but mixed acids such as aqua regia (three parts of hydrochloric acid and one part of nitric acid) and cyanide solutions can dissolve gold well. The melting point of gold is 1063°C. If the gold is heated to close to the melting point, the gold can be welded like iron. The fine gold particles can be melted into agglomerates, and the gold powder must be pressured to be welded together when the temperature is low. Gold can be alloyed with other metals, such as gold-silver alloy, gold-copper alloy, gold-silver-copper alloy. In addition, there are so-called gold amalgams. 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. The alloy is the product of the solidification of the metal after melting, so it has a homogeneous structure, while the natural gold is precipitated from the 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 layer. This coating layer is not only iron oxide, sometimes it may be some fine-grained gangue attached to the surface of the gold particles. This kind of coating not only affects the recognition of gold, but also makes it more difficult to process minerals (mercury amalgamation or cyanidation). Platinum Platinum is a white alloy made by smelting gold and other metals. Due to the scarce production of platinum, the high price, and the high melting point, most countries rarely use platinum to produce real K platinum. At present, in order to cater to consumers' demand for platinum, gold and palladium or nickel, silver, copper, zinc and other metals are smelted into a white alloy called 'k platinum'. The fineness of k platinum is the same as k gold, the mass of the bundle is 24, and the number of parts of the mass that gold occupies is the k number of'k platinum'. Such as 18k white gold and 14k white gold, the content of gold is 75% and 58.5% respectively. Platinum, also called platinum. Its English is platinum, and its abbreviation pt is generally used as the code name. wg is the abbreviation of white gold in English, that is, white gold. The gold that is engraved with 14kwg sold by the merchant is 14k white gold, which is a white alloy with 25% palladium or nickel added to the gold. It is actually a kind of karat gold, and the mass fraction of gold in it is' The k number of k platinum', the total mass is 24k. Such as 18k white gold and 14 white gold, the gold content is 75% and 58.3% respectively. Gold (au) is a yellow precious metal. To make jewellery, pure gold (ie 24k or 999.9 gold) or alloys of different degrees of pure gold (also called 'k gold') can be used. The most common are 18k gold (including 75% pure gold) and 14k gold (including 58.5% pure gold). The texture is soft and malleable, and can be refined into various shapes; but because it is not easy to form, most of the jewelry inlaid with diamonds or gems must use alloy (also known as 'K gold'). The alloy is harder than gold and can be made in a variety of shapes and designs; moreover, the color of karat gold is more variable: yellow gold, pink gold, green gold, white gold, blue gold, etc., the colors are really colorful! However, white gold has become more popular in recent years; yellow gold has to look for talented people. Previous: The maintenance of gold jewelry Next: The difference between pure gold and thousand pure gold
