Pyridine, 3-chloro-2-iodo-

Mercury is a highly toxic metal. It is a liquid at room temperature and has many unique chemical properties.
First, the chemical properties of mercury are relatively stable, and it is difficult to react with oxygen at room temperature and pressure. However, under heating conditions, mercury will combine with oxygen to form mercury oxide. The reaction is as follows:\ (2Hg + O ²\ stackrel {\ Delta }{=\!=\!=} 2Hg O\).
Second, mercury can react quickly with sulfur powder. Even in a room temperature environment, the two will combine to form mercury sulfide. This property is often used to treat spilled mercury to prevent mercury from volatilizing and causing harm. The reaction formula is:\ (Hg + S = HgS\).
Third, mercury can react with oxidizing acids. For example, when mercury is heated with concentrated sulfuric acid, mercury sulfate, sulfur dioxide and water are formed, and the chemical equation is:\ (Hg + 2H ² SO (concentrated) \ stackrel {\ Delta }{=\!=\! =} HgSO+ SO 2O ↑ + 2H 2O O\); mercury and concentrated nitric acid can react violently at room temperature to generate mercury nitrate, nitrogen dioxide and water, and the reaction formula is:\ (Hg + 4HNO 😉 (concentrated) = Hg (NO 😉) ³ + 2NO ³ ↑ + 2H2O O\); when reacted with dilute nitric acid, mercury nitrate, nitric oxide and water are formed, and the chemical equation is:\ (3Hg + 8HNO 😉 (dilute) = 3Hg (NO 😉) ▽ + 2NO ↑ + 4H2O O\).
Fourth, mercury can form amalgam with certain metals. The formation of amalgam changes the activity of mercury, and amalgam has important applications in metallurgy and other fields. For example, when refining metal ores such as gold and silver, mercury can be used to form amalgam to extract the metals.

Mercury, commonly known as mercury, is a unique liquid metal. Its physical properties are unique and detailed as follows:
- ** Normal temperature form **: Under normal temperature and pressure conditions, mercury appears as a shimmering silver-white liquid state, which is its significant physical property. Unlike common metals, which are mostly solid at room temperature, mercury's liquid form makes it unique among metals.
- ** Density **: Mercury has a high density, about 13.59 grams/cm3, far exceeding the density of many common substances. This property causes it to sink due to its high density when placed in other liquids. < Br > - ** Melting point and boiling point **: Mercury has an extremely low melting point of -38.87 ° C, so it is liquid at room temperature; the boiling point is relatively high, reaching 356.6 ° C. This range of melting point and boiling point allows mercury to remain liquid in a wide temperature range and is widely used in industry and science.
- ** Fluidity **: Mercury has very good fluidity. Due to its liquid state and low internal friction, it can flow rapidly in the plane, resembling flexible mercury beads. This property is also closely related to its liquid properties. < Br > - ** Conductivity **: Mercury has good electrical conductivity. As a metal, there are free electrons in it. Under the action of an external electric field, the free electrons move directionally to form a current, which can be used as a conductive medium in some electrical equipment.

"Tiangong Kaiwu" is a scientific and technological masterpiece written by Song Yingxing in the Ming Dynasty. The book elaborates on many things in detail. Brine occupies a key position in the ancient salt making process, and its main uses are as follows:
First, it is a raw material for salt making. In ancient salt making, brine was often boiled in brine to obtain salt. Many salt fields dug wells to obtain brine, and the brine content was quite high. For example, "In Yunnan and Shu provinces, far from the seashore, it is difficult to travel by boat, and the situation is high, and its salty veins are in the Yunzang area." This shows that Yunnan, Sichuan and other places often use salt wells to dig salt wells to make salt. Brine is introduced into salt fields, evaporated in the sun, or heated in a pot to boil, and the salt will precipitate. " Where a salt frying pan was called a prison basin in ancient times,... The following stoves burn, with more than twelve or thirteen eyes, and less than seven or eight eyes, frying this pan together. "It vividly depicts the scene of boiling brine in the pan to make salt.
Second, identify the quality of salt. Brine can test the advantages and disadvantages of salt. The book says:" Where salt melts in water, when it sees the wind, it is brine, and when it sees the fire, it is stronger. Where the brine method is tested, the chicken and peach kernels are tested. The brine taste is the saltiest, and the one that sinks to the bottom has not been tested. "It means that the salinity and salt quality of brine can be judged by the rise and fall of chicken and peach kernels in brine. If the chicken and peach kernels sink to the bottom, it indicates that the brine has high salinity and good salt quality, so as to ensure the quality of the salt made.
Third, it is used for alkali production. In addition to salt production, brine was also useful in alkali production in ancient times. Although it is not detailed in "Tiangong Kaiwu", it was known at that time that alkali-containing substances could be extracted from brine and used in daily life and production, such as textile dyeing, tanning and other industries, which is of great significance to promote the development of related industries.

Mercury is a highly toxic substance, but in Dan Dao and many ancient techniques, there is also a way to synthesize it.
One is to combine sulfur with mercury. In "Baopuzi Inner Part · Jindan", "Dan Sand burns into mercury, and the accumulation changes to Dan Sand". Dan Sand is mercury sulfide, which can be obtained by heating and decomposition. Mercury and sulfur are co-developed, and the two are combined to form mercury sulfide. This method needs to be handled with caution, because mercury is volatile and highly toxic in the process. When the research is combined, when it is in a closed vessel, it is slowly studied at low temperature to make the two fully blend to reduce the toxicity and volatility of mercury.
Second, it is combined with lead. The ancients said that lead can produce mercury. Mercury and lead are co-refined in a certain proportion, in a cauldron furnace, and calcined at an appropriate temperature. Lead can form an alloy with mercury, binding the activity of mercury and reducing its toxicity. However, this process also requires fine control of the heat and ratio. If the heat is too high, the mercury will fly away easily, and if the heat is insufficient, the combination of the two will not be sufficient.
Third, with the help of traditional Chinese medicine. Many herbal texts mention that some traditional Chinese medicines can be prepared with mercury. For example, Poria cocos, which are co-placed with mercury, may change the properties of mercury through specific processing methods. First, Poria cocos are ground into a very fine powder, placed in a porcelain jar with mercury, sealed and buried in the soil for several months. When taken out, the shape and properties of visible mercury have changed, and the toxicity may be reduced.
Fourth, in the alchemy cauldron, a variety of minerals are co-refined. For example, mercury, realgar, orpiment, saltpeter, etc. are co-refined. In a special alchemy cauldron, various substances are added in sequence according to a certain formula, and calcined alternately with civil and military fire. Realgar and orpiment contain arsenic sulfides, saltpeter is a strong oxidant, and various substances interact in the cauldron. Under complex chemical reactions, mercury may form new compounds, and its toxicity and volatility change.
However, it needs to be understood that even if there is such a method of synthesis, the highly toxic nature of mercury is difficult to change, and ancient operations are also risky. Today, people should dispose of mercury according to scientific and safe methods. Do not try ancient methods easily, so as not to endanger life and the environment.

When storing and transporting "alum", there are many things to pay attention to. Alum is dry and easy to absorb moisture and deliquescence. Therefore, the storage place must be dry and ventilated to prevent it from getting damp and qualitative changes and losing its original effect. Storage containers should also be selected carefully. Porcelain jars, ceramic jars and other materials should be used. Because of their stable nature, they do not chemically react with alum, which can preserve the purity of alum. Do not use iron or copper containers. Metals are easy to react with alum, causing its composition to change and affecting quality.
As for transporting alum, extra care should be taken. During handling, it should be handled with care to avoid collision and falling, otherwise the alum body will be broken, which will not only affect the appearance, but also accelerate its deliquescence. During transportation, it is also necessary to take good protection to shelter from the wind and rain and prevent rain from leaching. In case of bad weather, it is especially necessary to deal with it properly, or temporarily shelter from wind and rain, or strengthen cover protection to ensure that the alum is not damaged by moisture.
In addition, alum has certain toxicity. When storing and transporting, it should be stored and transported separately from food, medicine, etc., to prevent confusion and misuse, endangering the safety of humans and animals. The surrounding environment should also avoid children and irrelevant personnel from approaching at will, so as not to accidentally touch and eat by mistake, which will lead to major disasters. In short, the storage and transportation of alum requires caution at all times to ensure its quality and avoid its harm.