4-Pyridinecarboxylic acid, 2-fluoro-

The river, its sour, has a genus of cold, bitter, and sweet.
The acidic things in Guanfu River are mostly cold. Because the river gathers, the water moisturizes yin and coagulates, and its qi is cold, so the acid is affected by it, and it has a cold nature. Those who are cold can clear heat and reduce fire, and relieve the dryness and heat in the body. If people invade the body due to heat, they are thirsty and unbearable, and they get sour and cold things in the river, such as drinking nectar, the dryness and heat can be slowed down.
As for the bitter taste, the river acid may also have it. Bitterness can be dry and wet, and it can strengthen yin. As for the human body, when moisture accumulates, the bitter taste of river acid can help the spleen and stomach to transport and remove damp And the bitter taste strengthens the yin, which can nourish the yin liquid of the human body and make the yin calm and yang secret.
And those who have a sweet taste, Jiang acid also contains this property. Gan can replenish, can reconcile, and can slow down. The sweetness of Jiang acid can nourish qi and blood, and fill qi and blood. In case of visceral disharmony and inversion of qi, Jiang acid can adjust the sweetness of qi and make it smooth. If it is an emergency, the pain is urgent, and the sweetness slows down, it can relieve pain and soothe people's minds.
The things of Jiang acid, their cold, bitter, and sweet nature, have their own merits in the way of health and treatment of diseases. It is sincerely a gift of nature and a wonderful product of health.

Mercury is a highly toxic substance, which is very harmful to the human body, and arsenic is also a common poison medicine. Although the specific method of making mercury and arsenic is not detailed in "Tiangong Kaiwu", it is also recorded in ancient books in the traditional way of making this substance.
Mercury, the ancients often made it from dansha (mercury sulfide) as raw material. The color of dansha is vermilion, and its nature is yang. The method is mostly to put dansha in a closed vessel and calcine it with fire. The dansha is decomposed by heat, and mercury gas escapes, and the mercury gas is condensed when cold, resulting in a mercury liquid. In "Baopuzi Inner Chapter", there is the saying "dansha burns into mercury, and the accumulation changes into dansha". It is the wonderful transformation of dansha and mercury. The content of mercury in Geyin Dansha is quite high, and it can be extracted by this method to obtain mercury.
As for arsenic, it is often prepared from arsenic-containing minerals such as arsenopyrite (arsenopyrite) or realgar. The arsenopyrite and realgar are roasted, and the components of arsenic are oxidized to form arsenic trioxide, which is arsenic. The ancients mostly roasted by the local method, heating the arsenic-containing minerals in places with poor ventilation. During the process, the oxides of arsenic are sublimated and collected in the condensation place to obtain arsenic. However, this process is extremely dangerous, because the compounds of arsenic are highly toxic, and if they are not careful, they will be poisoned.
It should be noted that both mercury and arsenic are extremely toxic. The ancients made them, or used them for medicine, alchemy, etc. However, if it is used carelessly, it will harm lives. Today, science is prosperous, and there are strict regulations for the use of this highly toxic thing to prevent harm to everyone.

To make the carboxylic acid, there are various methods, which are described in detail as follows.
First, the method of oxidation by alcohols. Take a suitable alcohol and add a suitable oxidizing agent, such as a mixture of potassium dichromate and sulfuric acid, or potassium permanganate. Alcohol can be gradually converted into aldehyde during the oxidation process, and then oxidized to carboxylic acid. For example, ethanol, under the action of potassium dichromate and sulfuric acid, first forms acetaldehyde, and then further oxidizes to obtain acetic acid. This is a common way, the reaction is relatively easy, and the raw materials are relatively easy to obtain.
Second, the method of hydrolysis of nitriles. Select a specific nitrile and hydrolyze it in an acid or alkali environment. When nitrile is hydrolyzed, the cyanyl group is gradually converted into a carboxyl group. Such as acetonitrile, hydrolyzed under acidic conditions, acetic acid can be obtained. Although this method is slightly complicated, its selectivity is quite high. If the raw material nitrile is easy to prepare, it is also a good strategy.
Third, the carboxylation method of halogenated hydrocarbons. The halogenated hydrocarbons are used as the starting materials and react with metal magnesium to form Grignard reagents. Grignard reagents are extremely active and can react with carbon dioxide. After acidification, carboxylic acids can be obtained. For example, bromoethane and magnesium generate ethyl magnesium bromide, which is then reacted with carbon dioxide to obtain propionic acid after acidification. This approach can prepare carboxylic acids of different structures according to the structure of hal < Br >
Fourth, aldehyde oxidation method. The aldehyde has strong reductivity, and can be converted into carboxylic acid with weak oxidants such as Torun reagent, Feilin reagent, or strong oxidants such as hydrogen peroxide, oxygen, etc. If acetaldehyde is oxidized by oxygen, acetic acid can be obtained. This method has mild conditions and simple operation, and is widely used in industrial production.
All these methods have their own advantages and disadvantages. In actual preparation, it is necessary to carefully choose the appropriate method according to the availability of raw materials, the difficulty of reaction conditions, and the purity requirements of the product. Only then can the carboxylic acid be efficiently obtained.

The price of caramel in the market varies according to quality and supply and demand. In the past, the art of caramel making was simple, and its ingredients were mostly taken from millet, which was pounded, boiled, and fermented to obtain sweetness.
In today's city, the variety of caramel is very diverse. If it is ordinary, the quality is plain and the taste is pure, and the price per catty is about ten to twenty or thirty dollars. This is a common folk food. It is used in restaurants and ordinary households in Lu Lane to add flavor to the diet, or to accompany the cakes, so the price is close to the people.
However, if it is refined, the materials are well selected, or it is accompanied by precious fruits and fragrances, which have been carefully crafted by skilled craftsmen, its taste is better and the quality is also delicate. This kind of caramel is expensive at the market price, or to fifty or even a hundred dollars per catty. Gai is expensive because of its fine materials, and it is mostly supplied to rich families, or as a gift, which is not often enjoyed by the common people.
There are also those who are famous for their brands, which are famous far and wide, and their reputation is full of the market, and the price is also high because of it. Although the price of this kind of caramel is high, there are many people who seek it, and they believe in its quality, and everyone believes in its value for money.
As for the change in the price of caramel, it is also related to the prosperity of the year. If there is a good year, the grain is in the warehouse, and the materials are sufficient and the work is easy, the price will be stable and flat; if there is a disaster year, the grain harvest will fail, and the material source will be scarce, the price will increase. Therefore, if you want to know the price of caramel, you should not only look at its quality, but also check the supply and demand of the city in the sky.

In "Tiangong Kaiwu", the storage conditions of River-4 to its carboxylic acid are as follows:
River-4 to its carboxylic acid properties are more active, and the storage environment requirements are strict. It needs to be filled in a special porcelain urn, which needs to go through multiple firing processes and has a dense texture to resist its corrosiveness. The mouth of the urn must be tightly sealed with thick wax to prevent air and moisture from invading.
The storage place should be selected in a shady and dry place, and must not be placed in direct sunlight or humid places. Because sunlight exposure will increase the temperature, accelerate its chemical reaction and cause it to deteriorate; humid environment is easy to cause mildew on the outer wall of the porcelain urn, affecting the quality of carboxylic acid, and even penetrate the porcelain urn in severe cases, causing leakage.
In addition, flammable and explosive materials should be avoided around the storage place, because it is dangerous to encounter open flames or violent vibrations. It is also necessary to arrange regular inspections by special personnel to check whether the porcelain urn is damaged and the wax seal is intact. Once problems are found, they should be disposed of in time, so as to ensure that the carboxylic acid of River-4 is properly stored and its characteristics and quality are maintained.