pyridine, 2-bromo-

Mercury is a metallic element with unique chemical properties and has the following characteristics:
First, mercury has relatively moderate chemical reactivity. At normal temperature, mercury is difficult to react with oxygen, but when heated, it can combine with oxygen to form mercury oxide. This reaction can be expressed as: Mercury (Hg) and oxygen (O _ 2) under heating conditions form mercury oxide (HgO), that is, $2Hg + O _ 2\ stackrel {\ Delta }{=\!=\!=} 2Hg O $. This reaction demonstrates the property that mercury can be oxidized under certain conditions.
Second, mercury can form alloys with many metals, such alloys are called amalgams. If mercury is mixed with sodium, sodium amalgams can be formed. The formation of amalgam is based on the ability of mercury to dissolve other metals. This property is widely used in metallurgy and other fields. For example, some metals can be extracted by amalgam method.
Third, the reaction of mercury with acids is also characterized. Mercury does not usually react with non-oxidizing acids such as dilute hydrochloric acid and dilute sulfuric acid, because the metal activity order of mercury is after hydrogen. However, mercury can react with oxidizing acids such as concentrated sulfuric acid and nitric acid. Taking nitric acid as an example, the reaction of mercury with concentrated nitric acid will produce mercury nitrate, nitrogen dioxide and water. The chemical equation is $Hg + 4HNO (concentrated ) =\!=\! The reaction between mercury and dilute nitric acid produces mercury nitrate, nitric oxide, and water, with a chemical equation of $3Hg + 8HNO (dilute ) =\!=\!= 3Hg (NO < unk >) -3 + 2NO ↑ + 4H2O O $.
Fourth, mercury compounds also exhibit a variety of chemical properties. Many mercury salts have certain oxidizing properties, and some mercury compounds have poor stability and are easily decomposed when heated. For example, mercury oxide decomposes into mercury and oxygen when heated, that is, $2HgO\ stackrel {\ Delta }{=\!=\!=} 2Hg + O 🥰 ↑ $. The chemical properties of mercury include not only the reaction characteristics with oxygen, acids and other substances, but also the formation of amalgam and its compounds. These properties are of great significance and application in chemical research and industrial production.

Ethers are widely used in organic synthesis.
First, they can be used as solvents. "Tiangong Kaiwu" says: "All the materials used in the manufacture of boats and carts are mostly ether-soluble, which helps them to mix and dissolve." Ether has good solubility and can dissolve many organic compounds. In organic reactions, it is often used as a reaction medium, so that the reactants can be uniformly mixed, promoting smooth and efficient reaction.
Second, it has important applications in the strategy of protecting groups. As described in the book: "To protect the specific function of something, you can use ethers to form a protective state." Some organic molecules contain multiple functional groups, and if you want to perform a specific reaction on one of them, you can first protect the other functional groups by etherification reaction. After the required reaction is completed, the protective groups can be removed, so that the target reaction can be accurately achieved.
Third, ethers can also participate in organic synthesis reactions. "Ethers combine with various substances and often cause novelization." For example, in the Claisen rearrangement reaction, allyl aryl ethers are rearranged into o-allyl phenols when heated, which plays a significant role in building carbon-carbon bonds and synthesizing phenolic compounds. Another example is the Williamson synthesis method, which is an important means to synthesize asymmetric ethers by reacting halogenated hydrocarbons with sodium alcohols. It can design and synthesize ether compounds with specific structures according to needs, and is of great significance in the field of organic synthesis.

One of them is the need for high-quality materials. It is necessary to make high-quality gold, such as high-quality metal, whose proportion also needs to be high-quality. Take the best of the best, and increase the flow of light-making. In the past, we used a ratio of seven to three, so that the sound could be clear and the ground could be fixed.
The second is the foundation of mold-making. First, use mud or wood to carefully shape the mold. Its shape needs to be adjusted, and it needs to flow. The micro-scale of the mold cannot be ignored. The mold is made, and the sand is applied to it, and the sand is overturned, so that the sand is closely adhered. This is the sand mold. Or if there is a mold maker, it is soft and easy to carve. To be molded, it is made of high-quality gold, which is transformed when it is encountered, and the gold is molded into the mold. This method is also lost.
Third, melting. Set up a fire, set the gold in the crucible, and calcined it with fire. When the gold is molten, its color is not good, and the light is dazzling. It is very important to grasp the heat. The fire is fierce, and the fire is weak. Inject the molten liquid into the mold with the crucible, and the work needs to be fast, so that the molten liquid can quickly fill the various voids of the mold.
Fourth, dressing is good. When the piece is cold, be careful of the mold, the shape of this product has been formed. However, the surface may be rough, rough or uneven, and it needs to be trimmed with tools such as knives and grinding stones to make the surface smooth and perfect. Or engrave flowers and text on it to add its beauty and culture. In this way, a delicate method is achieved.

Mercury is one of the hardware, and its physical properties are very unique.
Looking at its form, under normal circumstances, mercury is in a liquid state, flowing like silver, with a dazzling luster, just like the moon, which is very different from other things that are mostly solid. This fluidity allows it to be shaped with things, and it can change flexibly in a container, without a fixed state.
When it comes to density, the density of mercury is quite large, far exceeding that of ordinary liquids. Compared with water, mercury is several times heavier than water. If you take an appropriate amount of mercury and put it in the same container with water, mercury will sink to the bottom of the water, like a rock falling from water. This characteristic is also a significant sign of it.
As for the melting point and boiling point, the melting point of mercury is extremely low, about -38.87 ° C, which is a liquid state at room temperature. And its boiling point is not high, at 356.6 ° C. With a little heat, it can easily turn into a gaseous state, curling and rising, like invisible smoke.
Mercury's thermal conductivity and electrical conductivity are also unique. Its thermal conductivity is good, heat transfer is fast, like a messenger, which can quickly send heat energy to various places. As for electrical conductivity, mercury is also a good conductor. When the current passes through, it flows unimpeded, like a duck to water.
In addition, the surface tension of mercury is very strong, on the plane, it can gather into droplets, round like beads, and not easy to disperse, like silver beads scattered, shining, beautiful.
To sum up, the physical properties of mercury are unique and wonderful. In the forest of matter, it is unique and elegant, and it is also a curiosity of the ancients. It has its extraordinary use in many fields.

"Tiangong Kaiwu" says that when silver (ingots) are used in melting and casting, many matters need to be paid attention to.
When melting and casting, the first heat is controlled. The size and duration of the fire are all related to the fineness and texture of silver. If the fire is too intense, the silver is easy to fly and damage, causing its weight to decrease, and the fineness or change; if the fire is insufficient, the silver is difficult to melt evenly, and impurities are difficult to remove, affecting the quality. Therefore, the smelter must carefully observe the heat to achieve the best melting and casting effect.
Furthermore, the choice of utensils is also the key. The crucibles, casting molds, etc. used must be resistant to hot topics and uniform in texture. If the crucible is not heat-resistant, there may be a risk of cracking between melting and casting, causing the silver liquid to spill, which will only increase the loss; if the texture of the casting mold is uneven, the surface of the cast silver ingot may be uneven, which will affect the appearance and specifications.
Whether the silver material is pure or not should not be ignored. Too many impurities not only reduce the purity of silver, but also cause adverse reactions during melting and casting, such as bubbles, bumps, etc. Therefore, before melting, when carefully checking the silver material, try to remove impurities to keep the silver pure.
The operation process also needs to be rigorous. When melting silver, do not stir at will to prevent the silver liquid from splashing and hurting people, and ensure uniform melting. When injecting into the casting mold, the speed and height are all exquisite. If the speed is too fast, it is easy to cause the air in the casting mold to not be discharged and form pores; if the speed is too slow, the silver liquid may condense first, which will affect the forming. Improper injection height will also make the surface of the silver ingot uneven.
The use of silver melting casting, from the heat, utensils, silver materials to the operation, all links are interconnected, and the smelter needs to be careful in order to cast silver ingots with good color, uniform texture and beautiful appearance, suitable for commercial and trade purposes.