4-pyridinecarboxaldehyde, 2,3,5-trichloro-

"Tiangong Kaiwu" says: "All nitrate is produced in Huayi, and China is specially produced in the northwest. Its quality changes with the soil, or yellow, white or red, or knot like flowers, or like guijiao, or like beans, all of which are bitter." Today there are four things, called saltpeter, sulphur, charcoal, and realgar. Among them, saltpeter, sulphur, and charcoal are the essential materials for making gunpowder.
Saltpeter has a dry and hot nature and can produce flames. It can be used in alchemy, medicine, and is also the key to gunpowder. Sulphur is flammable and has a special smell. It is used in gunpowder to support combustion, and it is also used in medicine and chemical industry. Charcoal is loose in texture and burns for a long time. It provides a carbon source in gunpowder, making it powerful for deflagration.
As for realgar, its sex temperature is toxic, and it is often used as medicine. It has the effect of detoxification and insecticide, dryness and dampness to remove phlegm. However, in the formula of gunpowder, it is rarely used, and it is not the main ingredient of gunpowder due to its toxicity and chemical properties.
The system of gunpowder is mixed with saltpeter, sulfur and charcoal in a certain proportion. Saltpeter accounts for about 75%, sulfur accounts for 15%, and charcoal accounts for 10%. The three are matched, and when ignited, it will explode, with amazing power. This formula has been optimized through long-term practice and is the crystallization of ancient Chinese wisdom.
Gunpowder is widely used in the military, as a weapon of war, changing the way of combat; in the civilian, it is used for festivals and fireworks to add a joyous atmosphere. Its invention and application, as one of the four great inventions of ancient China, had a profound impact on the process of world civilization.

Today there are four things, called carapace, which number four; called B, which number two; called C, which number three; called Ding, which number five, and has three mercury. The physical properties of these four things and three mercury are different, as detailed below.
The carapace is hard in texture and gray in color, and is often found between mountains and rivers. Its nature is calm, and it is stable when placed on flat ground. If it is hit by an object, it will have a crisp sound and wear resistance. Over the years, it is difficult to damage its shape. When heated, the temperature increases slowly, and it is difficult to change when exposed to water. It is insoluble in all common liquids.
B has different shapes, either lumpy or granular. Its color is bright and often shiny. The texture is soft, and the hand can slightly shape it. The specific gravity is light, and it can float more in water. Good thermal conductivity, touch it with the hand, and a cool feeling emerges. It is easy to ignite flames when burned, and is accompanied by a unique smell.
C things, in the shape of long strips, have a smooth surface. The color is greenish, and it has a warm feeling when viewed. Strong flexibility, can be twisted and continuous. The conductivity is slightly inferior to other things, but it is also useful. Corrosion resistance is acceptable, and it is not easy to rust in ordinary environments.
Ding, mostly in a fine state, with different sizes. The color is mixed, mainly yellow and white. The texture is loose, and it can be crushed when lightly pinched. Strong water absorption, placed in a wet place, it will soon become damp. Its weight is quite light, and the breeze can lift its dust.
As for tri-mercury, its state is special. It is a flowing liquid at room temperature, silver-white like a mirror, shining with luster. It has great density and can sink in many liquids. It is volatile and lasts in the air for a long time, and its amount is gradually decreasing. Thermal and electrical conductivity are of the highest quality. When heated, it expands rapidly, and when cooled, it shrinks significantly. And mercury is highly toxic, harmful to the body when touched and smelled.
These four substances and tri-mercury each have their own unique physical properties, and they all have their specific uses and values in various affairs, which cannot be ignored.

There are four things today, called methylmercury, two, three, five, and tribromine, all of which are related to the nature of chemistry. Methylmercury is also highly toxic. It is sexually active and often combines with various things. At room temperature, it is in a liquid state and shines with silver light, but its qi is invisible and highly toxic. If a person inhales it, the viscera will be damaged and the mind will be confused. Viewed, it is like a flowing silver, but it hides murderous intent.
Two, three, five, it is unknown what it refers to, and it is difficult to know its nature for the time being. However, in the field of chemistry, the order of numbers or substitute elements, or the state of chemical combination. If it is the order of elements, each has its own uniqueness, which is related to the emission of electrons and the change of valence state.
In the case of tribromine, bromine gas is aggregated in three numbers. Bromine, a dark reddish-brown liquid at room temperature, is volatile and has a strong pungent odor. Its chemical properties are active and highly oxidizing, and it is often used to take away electrons from other substances in chemical reactions. When it encounters metals, it can be synthesized into bromide; when it encounters organic substances, it can also cause changes in the reaction, or substitution, or addition, and its outer electronic state can induce changes in molecular structure.
Looking at these four substances, methylmercury and tribromine, are both active and harmful. The poison of methylmercury is very serious; the strength of tribromine is changeable in reaction and pungent in its breath. As for the second, third, and fifth, we can investigate their properties in depth until we know what they mean. Chemical substances are very wonderful. Although there is a risk of harm, they can be used well, and they can also be used for the benefit of the world.

To prepare tetravalent indium, di-, tri-, and quinti- halides, the synthesis method is as follows.
First take the element of indium, and choose a clean and dry reaction vessel. This vessel must be able to withstand the corresponding reaction conditions, and it is easy to observe and operate.
If the cationic indium compound is prepared, the indium can be reacted with strong oxidizing reagents. If an appropriate amount of nitric acid is used, slowly drop it into the container containing indium. During the reaction, pay attention to the intensity of the reaction, and adjust the reaction temperature and rate in a timely manner. When nitric acid reacts with indium, indium loses electrons and becomes positive. After a series of reactions and separation and purification steps, tetravalent cationic indium compounds can be obtained.
As for the synthesis of di-, tri-, and pentavalent trihalides, the halogenation agent is very important. Halogen elements or hydrogen halides are used as raw materials. If halogen elements, such as chlorine, are used, chlorine gas can be fully contacted with indium at a specific temperature and pressure. When chlorine gas reacts with indium in a certain proportion, trihalides of different valence states can be formed. To obtain divalent trihalides, the reaction conditions need to be precisely regulated, such as controlling the amount of chlorine gas and the reaction temperature, so that indium can be moderately oxidized. To obtain trivalent trihalides, the reaction parameters can be adjusted appropriately to promote further oxidation of indium. If you want to make pentavalent tri-halide, the reaction conditions are more severe, higher temperature and pressure are required, and the amount of halogenating agent needs to be accurately calculated, or with the help of a catalyst, to help the reaction proceed in the direction of generating pentavalent tri-halide.
After the reaction is completed, the subsequent separation and purification steps cannot be ignored. Distillation, recrystallization, extraction and other methods can be used to obtain a pure target product according to the physical and chemical properties of the product and impurities. In this way, it is also a method for the synthesis of tetravalent positive indium, di, tri, and pentavalent tri-halide.

"Tiangong Kaiwu" says: "Four-sided mango seeds, in February, March, and May, three branches are useful in many fields."
Three branches, in the field of papermaking, can be called a good material. Its leather fibers are flexible and slender, making it the best choice for making high-quality paper. In the past, the calligraphy and painting papers favored by many scholars and writers were mostly carefully processed from three branches of skin. This paper has excellent ink absorption and uniform ink. When writing and painting, the brushstrokes are smooth and the ink rhyme is full, which can perfectly present the charm of the creator. It is essential for cultural inheritance.
In the realm of medicinal use, three branches also have unique effects. It is gentle in nature and has the ability to detoxify and reduce swelling, stop bleeding and make muscles. Occasionally there are injuries in the mountains and forests, and applying medicine with three branches can often relieve the pain and promote wound healing. In the eyes of ancient healers, three branches are a good prescription for helping the world and saving people, and they have been used in folk medicine for a long time.
In the place of craft weaving, three branches also show their skills. Its branches are soft and tough, and can be woven by hand into exquisite bamboo baskets, baskets and other objects. These utensils are not only practical, but also beautiful in shape. They have both practical value and artistic value. They play a role in the inheritance of people's daily life and handmade art.
It can be seen that three branches play an important role in papermaking, medicinal use, craft weaving and other fields, bringing many conveniences and benefits to the world.