Mercury, lead, cadmium and other heavy metals have important uses in many industries involved in "Tiangong Kaiwu".
In hardware smelting, mercury is often involved in the separation of gold and silver. As written in the book, to obtain pure gold, the gold amalgam is heated, the mercury evaporates and the gold is retained, so as to purify. Lead plays a big role in casting money. In ancient times, when coins were cast, lead and copper were fused in a certain proportion, which could improve the texture and casting performance of coins, making them more durable and easy to cast.
In the field of ceramic production, lead can be used as a flux to reduce the firing temperature of ceramics, and can also improve the gloss and texture of ceramic glazes, making the ceramic surface smooth and bright.
As for cadmium, although it is not detailed in "Tiangong Kaiwu", it is known in later generations that its compounds have been used in the manufacture of pigments. Although there is no record of cadmium pigments being widely used in ancient times, it may be used for other metals, or there may be potential related processes to explore.
However, it is necessary to know that mercury, lead, and cadmium are all toxic. With the development of the times, people have deepened their awareness of its hazards. While taking advantage of its excellent characteristics, they have also paid more attention to preventing its adverse effects on the environment and human health. However, in ancient times, its important uses helped the development of many industries and promoted the progress of craftsmanship and the evolution of civilization.

Mercury is the only metal that is liquid at room temperature. It has the following physical properties:
First, in terms of color and form, mercury appears as a silver-white shining color, similar to flowing silver, uniform in texture and metallic luster, often in liquid form, with good fluidity. If it falls, it will quickly disperse into many small droplets.
Second, the density characteristics are significant, and its density is relatively large, about 13.6 times that of water. Therefore, when mercury coexists with water, it will sink directly to the bottom of the water.
Third, with regard to volatility, mercury has a certain degree of volatility at room temperature, and can slowly transform into mercury vapor and diffuse in the air. Although the evaporation rate is not extremely fast, this characteristic cannot be ignored, because its vapor is toxic.
Fourth, the melting point and boiling point are quite characteristic. The melting point of mercury is extremely low, about -38.87 ° C, so in a relatively low temperature environment, mercury can still maintain a liquid state; and its boiling point is about 356.6 ° C, relatively high boiling point.
Fifth, mercury has good electrical conductivity, which makes it used in some electrical equipment fields.
Water is indispensable to life and has many unique physical properties:
In appearance, pure water is colorless, odorless and transparent, like a clear mirror, allowing light to pass through smoothly, making the underwater objects clearly visible. Under normal temperature and pressure, water is shown as a liquid state, with good fluidity, and can change its own shape according to the shape of the container. The density of water reaches its maximum value at 4 ° C, which is about 1000kg/m ³. This property has a profound impact on nature. For example, when rivers and lakes freeze in winter, ice is less dense than water and floats on the surface, thus protecting underwater life from severe cold. The boiling point of water is 100 ° C (at standard atmospheric pressure). When heated to this point, water will vaporize violently, generating a large amount of water vapor; its melting point is 0 ° C. At this temperature, water will solidify from liquid to solid ice. In addition, water also has a high specific heat capacity, about 4.2 × 10 ³ J/(kg · ℃), which means that compared with other substances, when absorbing or releasing the same heat, the temperature change of water is relatively small, which plays a key role in regulating the earth's climate and maintaining the stability of the body temperature of organisms.
Stone sulfur mixture is a kind of fungicide used in agriculture made from quicklime, sulfur and water. In terms of physical properties, it generally presents a reddish-brown liquid state with the smell of rotten eggs, which is mainly derived from sulfur components. Stone sulfur mixture is relatively stable at room temperature, but its physical state and properties may change with temperature changes. Due to the fact that it is a mixture of various ingredients, there will be a certain amount of suspended particles, but after good cooking and treatment, these particles are relatively uniform in distribution, do not precipitate rapidly, and have a certain degree of suspension stability.

Mercury, lead, and cadmium are all common heavy metal elements in chemistry. Mercury is liquid at room temperature, volatile, and its vapor is highly toxic. Lead is soft in texture and has strong corrosion resistance. Excessive intake of lead can seriously endanger human health, affecting the nervous system, blood system, etc. Cadmium is also toxic and can accumulate in the body after entering the human body, damaging kidneys, bones and other organs.
When it comes to the stability of chemical properties, mercury can react slowly with oxygen at room temperature, and react faster when heated to form mercury oxide, so its chemical properties are not very stable. In the air, a layer of lead oxide or alkaline lead carbonate film is easily formed on the surface of lead, which can prevent further oxidation and show relative stability to a certain extent. However, under certain conditions, such as contact with acids and other substances, chemical reactions will still occur. Cadmium is relatively stable in dry air, and in humid air, a layer of cadmium oxide film will form on the surface, but this film has limited protective properties, and cadmium can react with a variety of acids, so its stability is not absolute.
In general, although mercury, lead, and cadmium can exhibit certain stability under some common environmental conditions, they are not absolutely stable in terms of chemical properties. They can chemically react with other substances under certain conditions, and because of their heavy metal properties, they are easily harmful to the environment and human health. Special caution is required when using and disposing.

To prepare 1-deuterium-2-hydrogen-5-bromopyridine, there are various synthesis methods, which are described as follows:
First, 2-amino-5-bromopyridine is used as the starting material. It is first reacted with a suitable diazonium salt reagent to form a diazonium salt intermediate. Then the intermediate is treated with a deuterium substitution reagent, and the reaction mechanism of diazonium group being replaced by deuterium can obtain the target product. This process requires attention to the precise control of reaction conditions, such as temperature, pH, etc., to prevent side reactions from occurring and affecting the purity and yield of the product.
Second, starting from 5-bromo-2-hydroxypyridine. First, the hydroxyl group is converted into a easily exiting group, such as a halogen atom or a sulfonate group. Subsequently, the nucleophilic substitution reaction is carried out with a deuterated nucleophile to realize the substitution of the hydroxyl group position by deuterium, and then 1-deutero-2-hydrogen-5-bromopyridine is obtained. In this path, the choice of nucleophilic reagents and the activity of the leaving group have a great impact on the reaction effect, which needs to be carefully considered.
Third, the cross-coupling reaction catalyzed by palladium. In the presence of palladium catalyst, ligand and base, the cross-coupling reaction of bromine-containing pyridine derivatives with deuterated alkenyl or aryl halide occurs. This method requires screening suitable catalysts and ligands, optimizing the reaction conditions, in order to improve the selectivity and efficiency of the reaction, and at the same time pay attention to avoid catalyst poisoning.
Fourth, use 5-bromo-2-pyridine formaldehyde as raw material. First, the aldehyde group is converted by a specific reaction, such as the formation of intermediates such as enol ethers or enamines. Then deuterated reagents are used to deuterate at specific locations, and finally the target 1-deuterium-2-hydrogen-5-bromopyridine is obtained through appropriate functional group transformation. This route requires careful regulation of the sequence and conditions of each step of the reaction to achieve the ideal synthesis effect.
All synthesis methods have their own advantages and disadvantages. In practical application, it is necessary to comprehensively weigh and choose according to the availability of raw materials, cost, difficulty of reaction operation, and requirements for product purity and yield.

Mercury, lead, and cadmium are highly toxic substances and must be carefully stored during storage and transportation.
First, the storage place must be solid and sealed to prevent leakage. Mercury is volatile, and if it escapes in the air, it will cause serious poisoning after inhalation. Therefore, when storing mercury, it should be stored in a special sealed container, and stored in a cool, dry and well-ventilated place, away from fire and heat sources. Although lead and cadmium are not volatile like mercury, they should also be properly stored in an airtight container to avoid chemical reactions caused by contact with air, moisture, etc., which will change its shape and increase the risk of leakage.
Second, when transporting, the packaging must be firm and reliable. Appropriate packaging materials should be selected, such as for mercury, commonly used thick-walled glass containers and sealed with paraffin wax, and then placed in a sturdy outer packaging box, surrounded by cushioning materials to prevent the container from breaking due to collision during transportation. When transporting lead and cadmium products, it is also necessary to ensure that the packaging can resist vibration, collision and extrusion, and the packaging should be clearly marked with warning signs, such as "toxic items" and "handle with care", so that transporters can understand their danger and handle them with caution.
Third, whether it is storage or transportation, relevant laws and standards must be strictly followed. Waste containing mercury, lead and cadmium should not be discarded at will or handled illegally, so as not to pollute soil, water sources, and endanger the ecological environment and public health. Those who are engaged in storage and transportation should also have professional training to be familiar with the characteristics, hazards and emergency treatment measures of such poisons. In case of sudden leakage, they can respond quickly and correctly to reduce losses and hazards. In this way, the safety of personnel and the environment can be guaranteed to the greatest extent during the storage and transportation of mercury, lead and cadmium.