1 Bromo 2 Chloro 4 Iodobenzene

Mercury, like mercury, has an indeterminate flow and is often liquid. Its silver-white color and metallic luster are the only metals that are liquid at room temperature. Mercury has a high density, about thirteen times that of water. It is soft and can be easily deformed. Its volatility is extremely strong, and it can slowly dissipate in the air at room temperature to form mercury vapor. This mercury vapor is highly toxic. If inhaled by the human body, it will seriously damage the nervous system, kidneys and many other organs. < Br >
Bromine is the only non-metallic element that is liquid at room temperature and pressure. Its color is red-brown, with a strong pungent odor, and it is highly volatile. The volatile reddish-brown bromine vapor is very toxic, and it has serious irritation and corrosion to the eyes and respiratory tract of the human body. The density of bromine is also greater than that of water, and it is slightly soluble in water. It is soluble in organic solvents such as ethanol and ether.
Astatine is a halogen element and is radioactive. Because of its extremely short isotope half-life, it is extremely difficult to obtain in nature. The chemical properties of astatine are similar to iodine, or it can form salts with metals. Its specific properties are limited by research, and it is difficult to clarify in detail. However, due to its radioactivity, it must be potentially harmful to organisms and will participate in specific chemical reactions. However, relevant studies are mostly based on theoretical speculation and a small number of experimental simulations.

Mercury is a liquid metal at room temperature. It has a silvery luster, is heavy and has good fluidity. Mercury has a high density, about 13.59 grams per cubic centimeter. Compared with many common metals, such as water, the density is only 1 gram per cubic centimeter, and the density of iron is about 7.87 grams per cubic centimeter. The density of mercury is much higher than that of water and iron, so it feels heavy in the hand.
Mercury has an extremely low melting point of -38.87 ° C and a boiling point of 356.6 ° C. This property makes mercury a flowing liquid at room temperature, resembling a smart silver bead. Its evaporation characteristics should not be underestimated. Even at room temperature, mercury will slowly evaporate to form mercury vapor. This mercury vapor is toxic and can cause damage to the nervous system, kidneys and other organs when inhaled into the human body.
Bromine is the only non-metallic element that is liquid at room temperature and pressure. Its color is red-brown and has a strong pungent smell. The density of bromine is about 3.119 grams/cubic centimeter. Although it is less dense than mercury, it is larger than that of common non-metallic substances. Its melting point is -7.2 ° C and boiling point is 58.78 ° C. Compared with the boiling point of mercury, it is more volatile and can often smell its pungent smell in the air.
White phosphorus, white or light yellow in color, is soft and waxy in texture. Its ignition point is extremely low, about 40 ° C, and it is easy to spontaneously ignite in the air, so it needs to be stored in water to prevent spontaneous combustion. White phosphorus is highly toxic, and can be seriously poisoned by ingestion or skin contact. The density of white phosphorus is about 1.82 grams/cubic centimeter, which is higher than that of water, so it will sink in water. These three substances, mercury and bromine are liquid, and white phosphorus is solid at room temperature, but they all have unique physical properties, either toxic or flammable. When using and storing, special care is required.

In organic synthesis, benzene, chlorine, bromine, iodomethane, etc. have unique uses.
Benzene, the representative of aromatic hydrocarbons, has a cyclic conjugated structure. It can be used as a solvent, and many organic reactions rely on it to dissolve the reactants, making the reaction uniform and efficient. In organic synthesis, it is a key raw material. In the Fu-G reaction, benzene and halogenated hydrocarbons or acyl halides, catalyzed by Lewis acid, can introduce alkyl or acyl groups into the benzene ring, and many aromatic derivatives, such as ethylbenzene, acetophenone, etc., are widely used in the synthesis of medicines, fragrances, and materials.
Chlorine, an active non-metallic element, is often introduced into organic molecules as In the preparation of chlorinated hydrocarbons, alcohols react with thionyl chloride, phosphorus trichloride, etc., and the hydroxyl groups are replaced by chlorine. Chlorinated hydrocarbons are important intermediates in nucleophilic substitution and elimination reactions. Polyvinyl chloride can be polymerized to obtain polyvinyl chloride (PVC), which is a common plastic. Chlorinated organic compounds are also used to synthesize pesticides, such as DDT (although partially banned due to environmental problems), using chlorine atoms to change the chemical properties and biological activities of organic compounds.
Bromine, similar to chlorine, the introduction of bromine atoms can change the properties of organic compounds. Bromohydrocarbons are widely used in organic synthesis, such as the preparation of Grignard reagents. Bromohydrocarbons react with magnesium in anhydrous ether to form Grignard reagents, which can react with Some bromine-containing flame retardants, with the flame retardant properties of bromine elements, improve the fire resistance of materials.
Iodomethane, simple halogenated hydrocarbons, methylation reagents. React with alcohols, phenols, amines and other active hydrogen-containing compounds to introduce methyl groups to form methyl ethers, methyl phenol ethers, methylamines, etc. In drug synthesis, iodomethane is often used to methylate active groups to change the molecular properties of drugs, such as regulating drug fat solubility, stability and biological activity.
These four are all important roles in organic synthesis, laying the foundation for the creation of rich and diverse organic compounds.

Mercury, alum, and arsenic are all commonly used in ancient times, and their production methods are exquisite. The details are as follows:
** Mercury production method **:
In ancient times, mercury was obtained, mostly from Dan sand. "Baopuzi · Inner Chapter" says: "Dan sand burns into mercury." That is, Dan sand (mercury sulfide) is decomposed by heating to obtain mercury. The method is to first put Dan sand in a closed cauldron and heat it slowly with charcoal fire. When Dan sand is heated, it decomposes into mercury and sulfur. Mercury is liquid and volatile when heated. Sulfur reacts with oxygen in the cauldron to form sulfur dioxide and escape. Later, by condensation, the mercury vapor is liquefied by cold and converges at the bottom of the cauldron, and can be collected.
** Preparation method of alum **:
There are many kinds of alum, take green alum (ferrous sulfate crystal) as an example. The common preparation method is to mine the stone containing iron ore, crush it, pile it in the open air, and gradually weathering the ore after sun and rain. Among them, iron oxidizes and combines with sulfate to form ferrous sulfate. Then the weathered ore is immersed in water, and ferrous sulfate dissolves into it to obtain a solution. The solution is heated and evaporated. When the water is reduced and cooled, ferrous sulfate crystals precipitate, which is green alum. There is also alum (potassium aluminum sulfate dodecahydrate), mostly taken from alum. The alum is broken and roasted to convert the potassium, aluminum and other components into soluble salts. After water leaching, filtration, evaporation, crystallization and other processes, alum can be obtained.
** Method of making arsenic **:
Arsenic, that is, arsenic trioxide, is mostly made of arsenopyrite (arsenopyrite). The arsenopyrite is first selected to remove impurities. Then it is placed in a furnace and heated in isolation from the air, and the arsenopyrite decomposes into arsenic and iron sulfides. The arsenic evaporates, collects, and is heated in full contact with the air, so that the arsenic is oxidized into arsenic trioxide, that is, arsenic. "Compendium of Materia Medica" contains: "Pi, the sex is as fierce as Pi, hence the name. The name of the living is Pi Huang, and the name of the refiner is Arsenic." It can be seen that arsenic is refined from raw arsenic, and the refining process requires careful operation. Due to its severe toxicity, a little carelessness can endanger life.

The genus of cauldron and arsenic are both poisonous medicines. They should be used with caution and care. They are related to life and safety and cannot be ignored.
Cauldron sand is hot and poisonous. External use can erode sores and remove rot. However, excessive or improper use will cause skin ulceration and internal invasion of poisonous evil. When applying medicine, carefully review the symptoms and accurately control the dose. If the disease of sores is not extremely serious and the rotten flesh is difficult to remove, it should not be used easily. And cauldron sand is quite irritating to the skin. After use, you need to pay close attention to the skin's reaction. If there is redness, swelling, severe pain, and ulceration, wash it with water as soon as possible and seek medical treatment.
Besides arsenic, its poison is especially strong, and it can be taken internally to rob phlegm and cut malaria. However, it is only used for serious diseases and diseases, and it must be processed to reduce the poison, and the compatibility should be cautious. Ordinary people misuse it, or if it is slightly overused, it will cause abdominal pain and diarrhea, cold limbs, and even life-threatening. Even if doctors use it, they should also weigh the pros and cons, and the identification will be accurate, while the disease stops. When storing arsenic, they must use a sturdy weapon, strictly seal it, and keep it out of the reach of children to prevent accidental ingestion.
All poisonous medicines should be strictly regulated in their procurement, storage, and use. The purchase needs to go through legal channels and have complete procedures; the storage should be handled by a special person, stored in categories, and marked with toxicity labels; when using, the doctor should have a clear doctor's order, and the patient should follow the teachings. Do not increase or decrease the dose or change the usage by yourself. If you are not careful, disaster will come, endangering your life. Therefore, when using poisonous medicines such as sand and arsenic, you must be careful to ensure safety.