2-(Thiophen-2-yl)pyridine

In the category covered by "Tiangong Kaiwu", "lead-2-based" (this expression has no corresponding in the original text, and it is temporarily speculated that it is related to zinc smelting and other related processes), its main uses have the following aspects.
First, in the field of metal smelting and casting, lead is often used in combination with copper and other metals to make alloys. Such as brass, it is an alloy of copper and zinc (Ulead). Brass has better mechanical properties than pure copper, increased hardness, increased strength, and more corrosion resistance. In ancient times, brass was widely used in the manufacture of various appliances, such as large ritual vessels such as Zhongding and daily household utensils such as pots and pans. Due to its beauty and durability, the cast weapon not only has excellent texture, but also has a golden color and is quite beautiful. Whether it is in solemn occasions such as sacrifices, or in the daily life of ordinary people, there are brass products.
Second, in the manufacture of weapons, lead also plays an important role. Alloys made of lead can be used to build weapons, making weapons more tough and sharp. For example, on the edge of some swords, by adding lead in a reasonable ratio, the hardness and toughness of the edge can be improved, and it is more lethal and durable in actual combat. It enhances the performance of weapons in the process of slashing, blocking, etc., and adds weight to the victory and defeat in war.
Third, in the field of architectural decoration, lead and its alloy products are also used. For example, some decorative components on buildings are cast with lead alloy, which can maintain the beauty and integrity of architectural decoration for a long time by using its good corrosion resistance. Some decorative parts of palaces and temples, such as door knockers, decorative beasts, etc., are made of lead alloy, which not only adds a sense of majesty and solemnity to the building, but also resists the erosion of time, and can still be well preserved after years.

Arsenic is refined from letter stone, and its main chemical composition is arsenic trioxide ($As_2O_3 $), which is highly toxic and may endanger life if ingested in small amounts. It must not be easily touched or eaten.
Arsenic is often white powder in appearance, light and delicate, like frost and snow, so it is named "arsenic". In terms of its physical properties, arsenic is solid at room temperature and pressure, and its melting point is relatively low, about 320 ° C. When heated, arsenic will sublimate, that is, it will directly change from a solid state to a gaseous state, which makes it easier to diffuse under certain conditions.
Arsenic is chemically stable, but in some specific chemical reactions, arsenic trioxide can participate in the reaction as an amphoteric oxide. When exposed to acid, it will exhibit the properties of alkaline oxides, react with acid to generate corresponding arsenite and water; when exposed to alkali, it will exhibit the properties of acidic oxides, react with alkali to generate arsenite and water.
From the perspective of toxic mechanism, after arsenic enters the human body, the arsenic element in it will combine with sulfhydryl groups in various enzymes in the body, thereby destroying the normal structure and function of enzymes and interfering with the metabolic process of cells. In particular, it has a huge impact on some key enzymes involved in cellular respiration and energy metabolism, which in turn leads to the inability of cells to obtain energy normally, dysfunction, and eventually damage to tissue and organ functions, which can cause death in severe cases. Therefore, when using or handling arsenic-related items, it is necessary to be extremely cautious and strictly follow relevant safety operating procedures.

Mercury (mercury-2-based) is a chemical substance. To understand its chemical properties, it is necessary to investigate its essence.
Mercury, that is, mercury, is liquid at room temperature and is a metal element with many properties. And (mercury-2-based), when thinking about the relationship between its structure and mercury. In terms of chemical understanding, the change of the group often leads to different properties.
Mercury is active and toxic to a certain extent. (Mercury-2-based) Due to the difference in structure, or in chemical reactions, it may have stronger nucleophilicity, due to the different distribution of electron clouds in the structure. In the field of organic synthesis, it can be used as a special reagent to participate in many reactions.
And the stability of (mercury-2-based) is also key. If its structure is stable, it is not easy to decompose under normal conditions; if the structure is not stable, it is prone to change, or release mercury elements, causing toxicity.
View its reaction with other substances, or it can be combined with electrophilic reagents to form new compounds. It may also have unique performance in redox reactions, or it may be an oxidizing agent or a reducing agent, depending on the specific situation.
The solubility of (mercury-2-based) may be different from that of mercury and related compounds. In organic solvents, or exhibit unique dissolution properties, which are significant for separation, purification and construction of reaction systems.
Overall, the chemical properties of (mercury-2-based) are different from those of mercury due to their different structures, which are of great value for exploration in chemical research and application.

There are three ways to combine the vectors of "di- (pentyl-di- base) ".
First, the law of parallelograms. If there are vectors\ (\ overrightarrow {AB}\) and\ (\ overrightarrow {AD}\), with both as adjacent sides to make a parallelogram\ (ABCD\), then the sum of the two vectors\ (\ overrightarrow {AC}\) is the diagonal of this parallelogram. Because the opposite sides of a parallelogram are parallel and equal, according to the properties of vectors,\ (\ overrightarrow {AB} +\ overrightarrow {AD} =\ overrightarrow {AC}\). This law is intuitive and clear, and has many applications in the synthesis of plane vectors.
Second, the triangle rule. Take the vectors\ (\ overrightarrow {a}\) and\ (\ overrightarrow {b}\), so that the starting point of the vector\ (\ overrightarrow {b}\) is named after the end point of the vector\ (\ overrightarrow {a}\), and then make the vector\ (\ overrightarrow {b}\) from the starting point of\ (\ overrightarrow {a}\) to the end point of\ (\ overrightarrow {b}\), then\ (\ overrightarrow {c} =\ overrightarrow {a} +\ overrightarrow {b}\). For example, in problems such as path planning, this rule can be used to calculate synthetic vectors. In the vector synthesis of "di- (pentyl-di- base) ", if it is regarded as two line segments connected, its composite vector can be obtained according to this law.
Third, the coordinate algorithm. Let the vector\ (\ overrightarrow {m} = (x_1, y_1 )\)，\(\ overrightarrow {n} = (x_2, y_2) \), then its sum vector\ (\ overrightarrow {m} +\ overrightarrow {n} = (x_1 + x_2, y_1 + y_2) \). If the coordinates of the "di- (pentamethyl-di- base) " vector in the coordinate system are known, the coordinates of the composite vector can be easily obtained by calculating according to this coordinate, and then the size and direction of the composite vector can be determined.
These three methods have their own lengths, and can be used to synthesize the "di- (pentamethyl-di- base) " vector depending on the specific situation.

"Tiangong Kaiwu" has written that alum is in the market, and its price often varies depending on the quality and time. Alum is an important chemical raw material, which is widely used and indispensable in many industries such as metallurgy, papermaking, printing and dyeing. Its market price is also affected by many factors such as supply and demand, origin, and quality.
Ordinary crude alum, at the market price, is about a few to dozens of copper coins per catty. This is because the refining process of crude alum is relatively simple, there are many impurities, and the quality is poor. It is mostly used in industries that do not require high purity, and the price is low.
If it is refined alum, with high quality and few impurities, its price should be much higher than that of crude alum. Each catty may reach more than 100 copper coins, or even higher. Because of its complex production process, it needs fine purification, which consumes a lot of manpower and material resources, and is suitable for high-end fields, it has strict quality requirements and is expensive.
Furthermore, the distance of the origin is also related to the price of alum. If the origin is close to the market, the transportation is convenient, and the cost is low, the price may be slightly cheaper; if the origin is remote, the transportation is difficult, and the cost increases greatly, the price will also rise accordingly.
The relationship between supply and demand is also the key to affecting the price of alum. If there is a peak season for alum use, or a sudden increase in demand for alum in some industries, and the supply is difficult for a while, the price will rise; conversely, if the demand is low and the supply is excessive, the price will decline.
However, prices in the world are fickle, and the price of alum is difficult to determine, depending on the specific situation at that time.