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 (abbreviated as Pt) shone brilliantly in the history of human civilization as early as 700 BC. At that time, the ancient Egyptians decorated their boxes with beautiful hieroglyphics in platinum. By 100 BC, South American Indians had successfully mastered the processing technology of platinum and made platinum jewelry with different styles. /kloc-In the 8th century, King Louis XVI of France especially favored platinum, calling it "the only precious metal worthy of the title of king". In modern times, the world-famous jewelry design Cartierfabergetiffany has created an immortal masterpiece with platinum. The world-famous Hope diamond is always set in a platinum chain.
At the beginning of this century, platinum has become the most popular precious metal in the United States. Its natural white luster has conquered the hearts of countless aristocratic families. After the outbreak of World War II, platinum has a very important military use. The US government once banned the non-military use of platinum and replaced it with platinum (an alloy of gold and other white metals), although platinum can never replace platinum in many aspects such as luster and hardness.
Today, the application of platinum in jewelry continues. Its three characteristics of rarity, purity and hardness and its natural white luster still fascinate men and women who pursue fashion.
Platinum is rare because the treatment of platinum is much lower than that of gold. So far, the global platinum reserves add up to only enough to fill a medium-sized room. It takes five months to extract one ounce of platinum from 10 ton platinum ore.
Platinum is pure because platinum ornaments usually contain 90% pure platinum and 10% platinum. In contrast, 18K white gold only contains 75% pure gold, and the white luster of platinum is natural and will not fade after long-term wear.
It is said that platinum is hard because of its high density and almost twice the strength of gold, and it is the best choice for inlaying all kinds of precision. Because of its good ductility, one gram of platinum can pull out a filament 2 kilometers long. The hardness of platinum makes it hard to wear and makes it as good as new.
The intrinsic value of platinum and its elegant luster have inspired countless jewelry designers, and the jewelry industry or fashion industry is keen to set off a "white wave" again. Cartier, a French designer, called platinum jewelry "the king of precious metals": GiorgioArmani used platinum wire in his evening dress; CalvinKlein also weaves his evening dress with platinum wire.
The design of platinum jewelry is also constantly innovating, among which Japan, as the largest market of platinum jewelry, is particularly representative. Japanese platinum jewelry works fine, from casting to polishing, without exception. The design style is both fashionable and subtle, and every embellishment is like a work of art.
As the second largest platinum jewelry market in the world, China needs to be further improved in design concept and processing technology to meet consumers' demand for personalized and fashionable jewelry.
Generally speaking, simple lines, exquisite ideas and fine processing are the current design fashion of platinum jewelry. Because of this, platinum design has been talked about by designers, because many modern works can be made by borrowing the silvery white and lines of the metal itself.
The passage of time did not take away people's love for platinum, but increased its beauty. The charm of platinum lies in its peaceful aftertaste from the inside out. Its value, firmness, truthfulness, purity and elegance all make people feel that platinum is worth owning.