6-fluoropyridine-3-carbaldehyde

"Tian Gong Kai Wu" has a saying: "All sturgeon, the ancient name of tuna. Its color is gray, the back has three lines of bone armor, the nose is long and the body, etc., the mouth is bottom and pointed, the belly is yellow and white, and the tail is as different as a stalk. Its nature floats on the water, and the night is heavy."
Eel, that is, yellow eel, has many main uses. First, it can be eaten. The eel meat is tender, the taste is delicious, and it is rich in nutrients. It is rich in protein, vitamins and minerals. The Compendium of Materia Medica also says that the eel is "sweet, warm, and non-toxic. It is used to nourish the middle and benefit blood, and treat the lips." In the field of diet and cooking, eel can be cooked into many delicacies, such as oil eel paste, with fresh eel as the main ingredient. After careful cooking, the eel meat is soft and tender, and the eel back is crispy. When served with hot oil, it "sizzles" and smells fragrant. Another example is the braised eel segment, with a bright red color and a mellow taste, which is deeply loved by everyone.
Second, eel also has medicinal value. Traditional medicine believes that eel is warm in nature and has a sweet taste. It enters the liver, spleen and kidney meridians, and has the functions of nourishing the middle and nourishing qi, nourishing blood and solidifying removal, warming the yang and benefiting the spleen, strengthening the essence and stopping bleeding, and nourishing the liver and kidney. For people who are weak, lack of qi and blood, and malnourished, eels are a good choice for dietary therapy and nourishment; they also have a certain adjuvant therapeutic effect on postpartum lochia and blood gas disorders.
Third, eels also play an important role in the ecosystem. Eels often live in rice fields, ponds, rivers and other waters, feed on various aquatic insects, small fish and shrimp, and are also prey to other large aquatic animals. They are in a specific position in the food chain and play an indispensable role in maintaining the balance of aquatic ecosystems.

Mercury, commonly known as mercury, is a metallic element with unique physical properties, as detailed below:
1. ** Status **: At room temperature and pressure, mercury is in a liquid state, which is significantly different from most metals. "Tiangong Kaiwu" said: "Where cinnabar and mercury, that is, the last stream of Dan sand, have the same properties as stones." Mercury can remain liquid at room temperature, making it easy to operate and observe, and has many applications in ancient alchemy and many experiments.
2. ** Color and Luster **: Mercury has a silver-white metallic luster, which is bright and dazzling. Although its luster is not detailed in the book, as a metal, it naturally has a unique luster of metals, which makes mercury easily identifiable visually.
3. ** Density **: The density of mercury is relatively high, about 13.6 g/cm3, much higher than that of common liquids such as water. Although the density of mercury is not explicitly mentioned in Tiangong Kaiwu, in practical applications, due to the high density of mercury, it can be used to make instruments such as hydrometers, or play a role in some separation experiments.
4. ** Fluidity **: Mercury has excellent fluidity, just like smart water. Because of its liquid state and low surface tension, it can flow rapidly and spread out on the plane. This characteristic requires special attention during alchemy and experimental operations to prevent its loss.
5. ** Melting point and boiling point **: The melting point of mercury is -38.87 ° C, and the boiling point is 356.6 ° C. The melting point is low, causing it to be liquid at room temperature; the boiling point is relatively high, and it can maintain a liquid state within a certain temperature range, providing stable conditions for many experiments and applications. Although the "Tiangongkai" does not mention the specific melting point boiling point value, the ancients must have an understanding of the state changes of mercury at different temperatures through long-term practice, and apply it to production and life accordingly.
6. ** Solubility **: Mercury is insoluble in water and most organic solvents, but it can dissolve some metals to form amalgam. As recorded in "Tiangongkai", when refining metals such as gold and silver, mercury can form amalgam with other metals, thereby separating and purifying metals. This is an important application of mercury in the field of metallurgy.

As for its chemical properties, although the ancient books have not been described in detail, it should have a certain stability according to common sense.
The leech lives on the bank of the rivers and lakes. After years of circulation, its long-term survival must depend on the stability of its own nature. The water is changeable, and the leech is in it, or affected by various factors such as water flow, water quality, and water temperature, but it still reproduces endlessly. Is this not a sign of its chemical stability?
Looking at its living environment, foreign bodies are mixed in from time to time, or when acid and alkali change, but the leech is not greatly disturbed, which shows that it has considerable tolerance to changes in the chemical environment. Although we have not measured its chemical properties in detail with precision tools, we can infer that the chemical properties of the leech are relatively stable from the perspective of its survival habits and environmental adaptability.
The leech is attached to the stone wood, and there may be special substances on its body surface to resist external erosion. This substance should have a certain stability in order to protect the leech. And the process of metabolism in its body presumably also requires the participation of substances with stable chemical properties to maintain the normal order of life. Therefore, in general, the chemical properties of the leech should be stable in order to survive in the complex environment of rivers and lakes and continue the race.

To make hexacyanoferric (ⅲ) salts, there are many methods, each with its own ingenuity.
One is the oxidation method. Take the solution of potassium ferrocyanide and slowly drop strong oxidizing agents, such as chlorine, hydrogen peroxide and the like. Taking chlorine as an example, it reacts with potassium ferrocyanide. Chlorine is strongly oxidizing, and iron (ⅱ) in the ferrocyanide root can be oxidized to iron (ⅲ), resulting in potassium hexacyanoferric (ⅲ) acid. The reaction formula is as follows: $2K_4 [Fe (CN) _6] + Cl_2 = 2K_3 [Fe (CN) _6] + 2KCl $. The raw materials of this method are common, and the operation is not complicated. However, it is necessary to pay attention to the dosage of oxidizing agent and the rate of dripping, so as not to overreact and cause impure products.
The second is the metathesis method. Mix a salt containing ferric ions, such as ferric chloride, with a solution of potassium cyanide. Iron ions and cyanogen ions can be quickly combined to form potassium hexacyanoferric (ⅲ) acid. The reaction formula is: $FeCl_3 + 6KCN = K_3 [Fe (CN) _6] + 3KCl $. This method is simple in steps and quick in reaction. However, potassium cyanide is highly toxic. Be careful when using it. Operate in a well-ventilated place and properly dispose of waste to prevent endangering the environment and personal safety.
The third is the direct synthesis method. Iron filings, carbon and potassium cyanide are used as raw materials and co-heated under specific conditions. Iron and carbon form a primary battery to promote the reaction, and the iron is gradually converted into potassium hexacyanoferric (ⅲ) acid. Although this method is easy to obtain raw materials, the reaction conditions are harsh, and precise temperature control and reaction time are required, and the equipment requirements are also high.
All these methods have advantages and disadvantages. In practical application, when choosing carefully according to specific needs, raw material availability, cost considerations and safety factors, in order to achieve the best synthesis effect.

Above the well of the market, the price of fish and shrimp often varies according to time, place and quality. However, looking at the past, you can also get its approximate range.
Shrimp, there are many kinds, different quality, and the price is also very different. High-grade fresh shrimp, with moist color and lively body and extremely delicious taste, in the city, the price ranges from tens of dollars to hundreds of dollars a catty. Most of these fresh shrimp are newly caught from rivers, lakes and seas that day, and the fresh air has not dissipated, so the price is high. If the shrimp is slightly inferior, or because it has been caught for a long time, or because of preservation, the freshness is slightly reduced, the price may be reduced to twenty or thirty dollars a catty. As for dried shrimp, the price depends on the size and quality of the shrimp. For large and high-quality shrimp, the price can be as high as 100 yuan per catty; for small and average quality, it also costs 30 to 40 yuan per catty.
The price of fish is not uniform. Common crucian carp and carp, usually, cost about ten to twenty yuan per catty. If the demand increases sharply during the season, the price may rise slightly, but it is not more than thirty yuan per catty. Grass carp, silver carp, etc., because of the large output, the price is relatively easy, usually around ten yuan per catty. However, such as bass, mandarin fish, etc., with their tender meat and mellow taste, the price is higher, often thirty or forty yuan per catty, if it is rare, the price may be even higher.
However, these are all rough numbers. The price of the market changes rapidly, or the production of fish and shrimp decreases sharply due to natural disasters, and the price will become expensive; or due to a bumper harvest, the supply exceeds the demand, and the price will drop. And the terroir is different in different places, and the price is also different. Therefore, if you want to know the exact price, you need to go to the market in person and inquire in detail before you can get it.