Tin "coat" - zinc
China is the first country in the world to discover and use zinc. According to Wang Tong’s chemical analysis of the chemical composition of ancient Chinese money in 1922, it was proved that it contained zinc. Then, in 1923, Zhang Hongjun conducted a special study on the problem of zinc used in ancient China, and successively published the "The Origin of Zinc in China" and "Re-discussing the Origin of Zinc in China." Based on the textual research on ancient Chinese literature and the analysis of Chinese money, he believed that China used zinc in the early Han Dynasty (first century BC).
China's zinc use begins with refining brass. Brass is a copper-zinc alloy. When China was in the Han Dynasty, there was such a law - no use of "pseudo-gold". According to research, this "pseudo-gold" is brass. In some of the works of the Northern and Southern Dynasties (AD 4th century), there was the word "meteorite". According to research, in ancient China, brass was called "meteorite". In some documents of the Tang Dynasty, it was recorded that brass was refined from "calcium" (zinc carbonate). "Tang Shu? Food and Food" said: "Xuan Zongshi (712-755), the world's furnace is ninety-nine, each furnace is cast 3,300 baht (ie silk), brass 21,200 jin" . The book "Tiangong Kaiwu" written by the Ming and Song Dynasties is more specific. It describes in detail the method of refining brass: "Every six pounds of red copper, four pounds of lead into the pot, which are melted into the tank, and taken out cold. It is made of brass.†The term “red copper†is copper, and “lead lead†is zinc.
China's refining of brass began in the early Han Dynasty. Then, when did the refining of metal zinc begin? According to research, it was at the latest in the Ming Dynasty. Ming "Tiangong Kaiwu" book "Hardware" chapter, a very detailed description of how to use "burning stone" to refining "lead lead", that is, using zinc carbonate to refine metal zinc. Zinc smelting is easier than ironmaking and copper smelting because zinc has a melting point of only 419 ° C and a boiling point of 907 ° C. Moreover, zinc is more easily reduced. If zinc ore and coke are put together and heated above 1000 ° C, the metal zinc is reduced from the ore by coke and boils like boiling water to become zinc vapor. By condensing this vapor, a very pure and beautiful metal zinc crystal can be obtained. In the past, the world thought that the earliest refining of metal zinc was in the United Kingdom, because the British published the patent document on the distillation of metal zinc in 1739. In fact, after the research of Chinese chemical history workers, this method was proved to be learned by the British from China around 1730.
According to Jinan black and white iron processing http:// research, in the 16th and 7th centuries, China produced a purity of up to 98% of metal zinc, which was transported by a large number of Western colonists represented by the East India Company to Europe. Later, even China The method of zinc smelting was also passed to Europe. So far, there are still people in Europe who call zinc "Dutch Tin". This is because the East India Company is opened by the Netherlands, Britain, France, Portugal and other countries. The appearance of zinc is similar to tin. The zinc is called "Dutch Tin". It goes without saying. In fact, the real name of this "Dutch tin" should be "Chinese zinc."
Zinc is a silvery white metal. Small iron buckets for water extraction, often seen with tin, have ice-like crystals on its surface, which is the crystal of zinc. Zinc is plated on the tin, mainly to prevent the iron from being embroidered. However, the strange thing is that zinc is more rusty than iron: a piece of pure metal zinc, placed in the air, the surface quickly turns blue-gray - rusting. This is because zinc combines with oxygen to form zinc oxide. However, this layer of zinc oxide is very dense, it can cover the surface of zinc tightly, and protect the zinc inside from rust. Thus, zinc is hard to corrode. Because of this, people put a layer of zinc on the surface of the tin to prevent iron from rusting. Every year, 40% of the world's zinc is used to make tin, made into various pipes, barrels, and so on.
Jinan black and white iron processing thinks that the tin metal is more durable than the tinplate: the tinplate breaks a bit and will soon rot; however, even if the tinplate breaks a large piece, it is not easy to be rusted. This is because the chemical nature of zinc is more active than iron. When the outside air and water "attack" to the tin, zinc first combines with oxygen, which protects the safety of iron. However, tin is more expensive than tinplate. In addition to making tin, metal zinc is also used to make outer casings for dry batteries. However, the zinc in the dry battery case is relatively pure. In addition, zinc is also made of copper and zinc alloy with copper - brass.
The most important zinc compound is zinc oxide, commonly known as "zinc white", which is a famous white pigment used to make white paint. Zinc oxide is white at room temperature and turns yellow when heated, and turns white again when it is cooled. Now, people use this feature to make a "color-changing thermometer" - measuring the temperature with its color change. Zinc is also an indispensable element in plant growth. Zinc sulphate is a "micronutrient fertilizer." It has been determined that in general plants, about one part per million of zinc is present, and some individual plants contain high levels of zinc, such as psyllium containing one ten thousandth of zinc, and celery containing five tenths of zinc. In some cereals, there is actually 12% zinc.
In the human body, zinc is also contained in more than one hundred thousandth. The most zinc-containing is the teeth (0.02%) and the nervous system. Interestingly, the fish transferred almost all of the zinc in the body to the eggs before the spawning period. The content of zinc in the earth's crust is about one in 100,000. The most common zinc ore is a sphalerite that shines with a silver-gray metallic luster. Its chemical composition is zinc sulfide. Nowadays, sphalerite is commonly used in the industry to smelt zinc. According to incomplete statistics, the world annual output of zinc in 1971 reached 3.7 million tons.
Jinan black and white iron processing by the way, zinc is often mistaken for lead, such as galvanized iron wire was mistakenly called "lead wire", galvanized iron sheet was mistakenly called "lead skin", the barrel made of white iron was mistaken Known as the "lead barrel", this should be corrected. I talked with relevant industry insiders. It is said that the base of tinplate may be worse than Q235, but it does not say the specific grade. The price is mostly lower than that of galvanized iron sheet---commonly known as "white iron". That is, a galvanized low carbon steel sheet (the thickness is generally between 0.44 and 1.2 mm). Not easy to rust. There are two kinds of flat plates and waveforms (corrugated). Commonly used to make roofing, pipes and various containers. Ungalvanized is commonly known as "black iron".
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