Mercury, lead, cadmium, etc. are all highly toxic metals, and although they have a wide range of uses, they also have many drawbacks.
Mercury was often used in alchemy in ancient times. Alchemists wanted to use it to refine elixirs of immortality. This was a false move, but everyone believed it at that time. In the field of medicine, mercury-containing medicines were used to treat diseases, such as some medicines for scabies. However, mercury is highly toxic and can damage the nervous system, kidneys, etc. Long-term exposure or ingestion can cause serious diseases.
Lead was often used in ancient times to make utensils, such as lead wine utensils, food utensils, etc. In writing, lead powder was also used for writing. However, when lead enters the human body, it can affect people's intellectual development, especially for children, which can cause learning disabilities, abnormal behavior, etc.
Cadmium, in the past, was used to make pigments, making the color of utensils more bright. However, cadmium poisoning can cause serious consequences such as kidney failure and skeletal lesions.
Although these highly toxic metals may have some uses in the past, their use has been strictly restricted in view of their serious harm to the human body and the environment. Due to the limitations of cognition, the ancients used these highly toxic metals, resulting in many adverse consequences. Today, we should be guided by science and treated with caution. We must not repeat the same mistakes in order to ensure human health and environmental peace.

Mercury is a highly toxic metal element. It is liquid at room temperature and volatile. Its many physical properties are particularly unique.
The melting point of mercury is -38.83 ° C and the boiling point is 356.73 ° C. This allows mercury to exist in a liquid state at room temperature. Its liquid form flows freely, like a smart silver liquid, with a shiny luster.
The density of mercury is quite high, reaching 13.59 g/cm ³. Compared with common metals, such as water, the density of mercury is only 1g/cm ³. The density of mercury is far higher, so it can sink to the bottom of the water, and the quality of mercury is more impressive under the same volume.
Mercury has good electrical and thermal conductivity, which makes it potentially useful in fields related to electrical and thermal conductivity. Although its electrical conductivity is inferior to that of good conductors such as copper and silver, the electrical conductivity of mercury is also indispensable in certain situations.
Furthermore, the surface tension of mercury is extremely high, so it is easy to form spherical droplets on solid surfaces and is not easy to spread. This property also makes it unique in some experiments and application scenarios. Although mercury has many special physical properties, it is highly toxic. The inhalation of volatile mercury vapor into the human body or through skin contact can cause serious damage to the human nervous system, kidneys, etc. Therefore, when using and handling mercury, it is necessary to exercise caution and follow strict safety procedures to prevent mercury poisoning.

The chemical properties of mercury, river, tin, and lead are different. Mercury is a liquid metal at room temperature, with a silver-white color, fluidity, and volatility. It is highly toxic. Its chemical properties are relatively stable, and it can react when it encounters strong oxidants. "Tiangong Kaiwu" says: "Where mercury is used again, it is called silver vermilion (that is, mercury sulfide)." This is an example of mercury reacting with sulfur to form mercury sulfide.
The river is not a single chemical substance, but a mixture of various substances, containing many ions, minerals and microorganisms. The dissolved calcium and magnesium plasma are related to the hardness of water. The chemical properties of the river are affected by the geology, climate, and human activities that flow through the region.
Tin is a soft metal with good ductility and corrosion resistance. At room temperature, its chemical properties are relatively stable. In case of strong acids and alkalis, chemical reactions will also occur. For example, tin reacts with hydrochloric acid to generate stannous chloride and hydrogen. "Tiangong Kaiwu" mentions the manufacture and application of tin ware, which shows its wide range of uses in life and depends on its stable chemical properties.
Lead is a heavy metal, soft and has a low melting point. Its chemical properties are relatively active, and it is easily oxidized in the air, forming a layer of lead oxide film on the surface. Lead can react with acids, such as dilute sulfuric acid to form lead sulfate and hydrogen. Many lead compounds are toxic and pose great harm to human health. " Although the chemical properties of lead are not described in detail in "Tiangong Kaiwu", the application of lead in ancient times was quite extensive, such as casting lead characters and lead-making devices, etc. However, its toxicity also needs to be carefully prevented.

"Tiangong Kaiwu" is a comprehensive work on agricultural and handicraft production in our country in ancient times. There are many exquisite records of the synthesis methods of mercury, lead, tin, arsenic and other substances involved.
The synthesis of mercury used to be extracted from Dan sand. In the case of Dan sand, that is, mercury sulfide, its color is vermilion, which is a common mercury-containing mineral. In "Tiangong Kaiwu", Dan sand is placed in a special furnace tripod and calcined at high temperature over charcoal fire. Dan sand is decomposed by heat, sulfur and mercury are separated, and mercury is turned into gaseous ascension, condensed when cold, and collected to obtain pure mercury. This process requires precise control of heat, temperature, and time. If there is a slight difference, the purity and yield of mercury will be affected.
The synthesis of lead is mainly derived from galena. Galena is a lead sulfide mineral. The ancients first crushed galena and placed it in a furnace for roasting. During roasting, lead sulfide reacts with oxygen in the air to generate lead oxide and sulfur dioxide gases. Later, lead oxide and coke and other reducing agents are placed in a furnace. Under high temperature, the coke reduces lead oxide, and the lead is replaced. After refining and refining, pure lead can be obtained. This process requires mastering suitable roasting temperature and reduction conditions to ensure the quality of lead.
The synthesis of tin is mostly made of cassiterite. The main component of cassiterite is tin dioxide. After the ancients mined cassiterite, they first enriched it through mineral processing to increase the content of tin in cassiterite. Subsequently, the enriched cassiterite is mixed with charcoal and other reducing agents, and put into the furnace for high temperature smelting. Under high temperature conditions, the charcoal and tin dioxide undergo a chemical reaction, and the tin is reduced and precipitated. After removing impurities and other processes, tin metal can be obtained. This process requires high sealing and temperature control of the furnace.
Arsenic, that is, arsenic trioxide, is often synthesized from arsenic-containing minerals. Arsenic-containing minerals are first roasted to convert arsenic into volatile oxides, which are collected by condensation, and then further purified to obtain arsenic. However, arsenic is highly toxic, and caution must be used during the synthesis process to prevent poisoning.
The synthesis methods recorded in "Tiangong Kaiwu" consolidate the wisdom and practical experience of the ancients and lay an important foundation for the development of chemical processes in later generations.

When storing and transporting poisons such as mercury, lead, and cadmium, the following things should be paid attention to:
First, it concerns the storage place. It is necessary to find a dry, cool and well-ventilated place, and must not be placed in a humid, high-temperature or direct sunlight place. Because moisture can easily cause poisons to rust and deteriorate, high temperature and direct sunlight or cause their volatilization to accelerate, increasing the risk of exposure. And the storage place should be kept away from fire sources, heat sources, and all kinds of flammable and explosive materials to prevent accidents. At the same time, obvious warning signs must be set up to make everyone aware of the presence of dangerous poisons here.
Second, about storage utensils. Use specially designed, well-sealed containers to contain poisons. Such as mercury, commonly used thick-walled glass containers or metal containers, and ensure that the seal is tight to prevent the volatile leakage of mercury. For solid poisons such as lead and cadmium, it is also necessary to choose suitable containers to avoid reactions with external substances. Key information such as the name, type and content of the poison should be clearly marked on the container to prevent confusion.
Third, the time of transportation. Be sure to take comprehensive protection and fixing measures before transportation. Make sure that the container is stable and will not collide or tip during transportation. Select appropriate means of transportation, and transport personnel must also be professionally trained to be familiar with the characteristics of poisons and emergency treatment methods. Transportation route planning should avoid densely populated areas and environmentally sensitive places. In case of leakage, harm can be reduced.
Fourth, follow regulations and procedures. Whether it is storage or transportation, it is necessary to strictly follow the relevant national laws, regulations and standard procedures. Do not act in violation of regulations to avoid serious consequences. Every step of the operation must be recorded in detail for future inspection and traceability. In this way, the safety of the storage and transportation of poisons can be guaranteed to the greatest extent, and people and the environment can be protected from harm.