In "Tiangong Kaiwu", (that is, kao sand, the main component of ammonium chloride) is quite widely used. It is used in the metallurgical industry and can be used as a flux. For example, when casting copper, adding kao sand can reduce the melting point of the metal, make the copper liquid flow more smoothly, and the casting is formed better. The texture of the casting is uniform, less defects, and the quality of the casting is improved.
In alchemy and pharmaceuticals, kao sand is also used. Ancient alchemists used kao sand to participate in the preparation of many alchemy prescriptions. In pharmaceuticals, kao sand can be compatible with other medicinal materials, or play the effect of softening and dispersing knots, which can treat diseases such as scrofula, sputum nucleus, etc.; or it has the power of eroding sores and removing rot, and has an auxiliary therapeutic effect on the later stage of carbuncle sore rot.
In leather processing, kao sand can be used for leather hair removal and softening. Soaking the leather in a solution containing kao sand can make the hair on the leather fall off more easily, and can improve the texture of the leather, making it softer and tougher, which is convenient for subsequent processing into various leather goods.
In addition, in the ancient printing and dyeing industry, kao sand can be used as a mordant. When dyeing fabrics, adding sands helps the dye adhere better to the fabric fibers, making the dyeing more uniform and firm, the color is also more vivid and lasting, and the quality of printing and dyeing is improved. In short, sands played an important role in many industries in ancient times, providing assistance for production and life.

1-Neon-2,4-diene-3-carbonyl-indole, this substance is a chemical substance, and its physical properties are quite characteristic.
Neon is a single-atom rare gas. Under normal temperature and pressure, neon is colorless and odorless, with extremely inactive chemical properties and few chemical reactions with other substances. Its melting point is -248.67 ° C, its boiling point is -246.08 ° C, and its density is slightly smaller than that of air. Neon glows orange-red when powered on, so it is often used in neon lights and other fields.
As for 2,4-diene-3-carbonyl indoles, this organic compound contains functional groups such as conjugated dienes and carbonyl groups, which give it specific physical properties. Generally speaking, it is mostly solid at room temperature and has a certain melting point. In view of the existence of conjugated systems, it has characteristic absorption in the ultraviolet region and can be used as a key intermediate in the field of organic synthesis. The conjugated structure also gives it certain electronic delocalization properties, which affect its physical and chemical behavior. The existence of carbonyl groups allows it to participate in many chemical reactions involving carbonyl groups, such as nucleophilic addition. Because its molecular structure contains multiple unsaturated bonds and cyclic structures, it has certain stability and rigidity, which affects its melting point, solubility and other physical properties. In common organic solvents, there may be a certain solubility, but the solubility in water is low, which is due to the hydrophobicity of the molecule.

In terms of halogenes, their properties are originally water, but the halogenes contained in them are not pure water. Halogenes are mixed with various minerals, so their properties are different from water.
As for dienes, they have a conjugated structure, which makes their electron clouds different from ordinary hydrocarbons. The existence of conjugated systems endows dienes with active chemistry, and they are easy to react with various reagents such as addition and polymerization, which is really unstable.
For carboxylbenzene, the carboxyl group is connected to the benzene ring, and the carboxyl group is acidic. The benzene ring has its unique electron cloud characteristics. The two affect each other, the carboxyl group makes the electron cloud density of the ortho and para-site of the benzene ring slightly reduced, and the electrophilic substitution activity of the benzene ring is slightly reduced; the benzene ring makes the hydrogen of the hydroxyl group in the carboxyl group more easily dissociate and enhances its acidity. However, overall, carboxylbenzene is still a relatively stable compound under common conditions, and it is not easy to initiate drastic changes.
To sum up, halogen is impure due to impurities, diene is active due to conjugated structure, and carboxylbenzene is relatively stable although it has group interaction. Therefore, among the three, carboxylbenzene has the most stable chemical properties, halogen is heterogeneous and variable, and diene is active and difficult to

In the ancient times, there was a method of boiling the sea. In the land of the sea, seawater was introduced into the large kettle, and it was boiled with firewood. When the water was steamed, the crystals were dissolved. This ancient method, however, consumed a huge amount of firewood. In the land of the sea, seawater was introduced into the large kettle, and it was boiled with firewood. When the water was steamed, the crystals were dissolved. This ancient method, however, consumed a huge amount of firewood. It is also used in the fields of the sea, and seawater was introduced into the fields. With the help of sunlight exposure and force blowing, the water was naturally steamed, that is, the crystals were placed in the fields. This method of boiling the sea saves firewood, saves effort, and is more convenient.
As for the production of 2,4-diene, it is necessary to use suitable raw materials of the compound. It is often used to control the reaction rate and other general components under the action of the catalyst of the refinement. Catalysis can make the reaction rate increase in the desired direction. If the degree is high, if the reaction rate is high or out of control, it will cause the number of side effects to increase. If the degree is low, the reaction rate will be low, and the amount of influence will be high. The same is true. The appropriate solution can promote the effective collision of the anti-reaction molecules, improve the reaction efficiency, and obtain 2,4-diene.
The fabrication of pyridine is exquisite. Usually the phase extracted from coal tar is the starting material, and it is also obtained by synthesis. In the process of synthesis, the raw material is first made into a specific reaction to form a medium substance. In this process, the mixture is then reversed in multiple steps, such as melting, boiling water, etc. Each step needs to be controlled by the grid, and the catalysts used are also different. In the reverse process, the materials are fully mixed, reversed, divided, and lifted. Only when the mixture is removed can we obtain the best pyridine. Therefore, the fabrication methods of pyridine, 2,4-diene, and pyridine each have their own methods, and they all need to be carefully studied according to the principle of chemistry in order to obtain the best.

Mercury, 2,4-diene, and 3-carbonyl steroids should pay attention to the following matters during storage and transportation:
Mercury is a liquid metal, which is toxic and volatile. When storing, a sealed container must be used to prevent the volatilization of mercury from escaping, causing environmental pollution and human harm. And it should be placed in a cool, dry, well-ventilated place, away from fire and heat sources, because high temperature will increase the volatilization rate of mercury. During transportation, it is also necessary to ensure that the packaging is tight and a leak-proof device is installed. In case of leakage, it can be covered with sulfur powder to form mercury sulfide and reduce toxicity.
2,4-diene substances, many of which have unsaturated bonds and are chemically active. Storage should be in a cool and dark place, because light and high temperature are prone to reactions such as addition and polymerization, which cause deterioration. Packaging materials must have good chemical stability and do not chemically react with 2,4-diene. When transporting, prevent vibration and collision to avoid damage to the package and cause leakage.
3-carbonyl steroids, some of which are biologically active, require strict storage conditions. It should be stored in a low temperature environment, often refrigerated or even frozen to maintain its structure and activity stability. Storage containers need to be dry due to moisture or hydrolysis and other reactions. During transportation, low temperature conditions should also be maintained, and thermal insulation equipment should be used to ensure that the temperature is suitable. At the same time, whether it is storage or transportation, it is necessary to make a good mark, indicating its characteristics, hazards and emergency treatment methods, so that relevant personnel can respond.