In "Tiangong Kaiwu", arsenic, or arsenic trioxide, is mainly used in the following aspects:
First, in the field of medicine, although arsenic is toxic, it can be used as medicine after being reasonably processed and used. Ancient doctors found that a small amount of arsenic can have a certain effect on certain diseases, such as the treatment of malaria. Many ancient medical texts such as "Compendium of Materia Medica" have records on the medicinal use of arsenic. Arsenic is used as raw material to make pills and powders. Under the premise of controlling the dosage, it may be effective in regulating the balance of yin and yang in the human body and treating difficult diseases.
Second, in agriculture, arsenic can be used as an insecticide. Because arsenic is highly toxic, it can poison and kill many pests, which is beneficial for protecting crops from insect attacks. Ancient farmers would apply an appropriate amount of arsenic to farmland to control locusts, crickets and other pests, so as to ensure crop yields. However, due to the high toxicity of arsenic, caution should be used to prevent serious harm to soil, water sources and humans and animals.
Third, in industrial production, arsenic also has its uses. For example, in some metal smelting processes, arsenic can be used as an additive to improve metal properties. In the manufacture of some special alloys, the addition of an appropriate amount of arsenic can optimize the hardness and toughness of the alloy to meet specific industrial needs. However, due to its toxicity, the use process needs to strictly follow the operating specifications to prevent harm to the environment and people. < Br >
It is necessary to make it clear that arsenic is highly toxic, and improper use can easily cause poisoning and even endanger life. Therefore, whether it is in medicine, agriculture or industrial applications, it is necessary to strictly control the dosage and use methods and treat them with caution.

The properties of the two kinds of lead are very different. Lead is heavy and soft, and its color is gray and moist. Its melting point is quite low, about 327 degrees, and when heated, it is easy to melt into a liquid and flow away amorphous.
The density of lead is very high, more than eleven times that of water. When you hold it in your hand, you feel that it is heavy and abnormal. Its chemical properties are relatively stable, and it is not easy to react with other things in ordinary environments. In case of strong acids and alkalis, it can also gradually respond.
As for ductility, although lead has it, it is inferior to gold, silver and copper, etc. It can be hammered into thin sheets, but it is difficult to be as thin as gold and transparent. And the conductivity of lead is not good, compared with other good conductors such as copper and aluminum, it is far from being able to match, so it is rarely used for conduction.
Lead is toxic and is well known to the world. If the human body inhales or ingests lead dust and lead compounds, it will harm the nervous, blood, and digestive systems for a long time. Therefore, the industry involving lead requires the most protection.
Eighteen taels of lead were used in ancient times for alchemy, casting tools, etc. However, today, because of its toxicity, it must be used with caution to prevent harm to life and the environment. The use of lead should be based on safety and environmental protection, so that its physical properties can be used by the world and avoid its harm.

Mercury is a highly toxic substance, and its chemical properties are relatively active and not stable.
Mercury, which is a liquid metal at room temperature, is silver-white and is also known as mercury. "Tiangong Kaiwu" has a saying: "Where cinnabar, mercury, and silver vermilion are originally the same thing, so those with different names are divided into rough, old and tender." Mercury is highly volatile, and can form mercury vapor at room temperature. This vapor is highly toxic and once inhaled, it is extremely harmful to the human body.
Mercury can form alloys with many metals, called amalgams. And mercury can react with oxygen. When heated, mercury will combine with oxygen to form mercury oxide. In addition, mercury can also react with acids, such as nitric acid, to form mercury nitrate and other substances.
Looking at its experimental performance and chemical properties, mercury is by no means a stable substance. It is easy to migrate and transform in the environment, posing a serious threat to the ecological environment and human health. Therefore, when using and handling mercury, extreme caution should be taken and strict safety procedures should be followed to prevent serious consequences such as poisoning caused by mercury leakage.

To make one percent of the eighteen dans of mercury, the methods are as follows:
First, choose the material to the point. For mercury, take pure and free products, such as silver-white in color, like beads in quality, and its nature is agile. The adjuvants also need to be excellent and the proportion is appropriate. If you take lead, choose its heavy and blue-gray in color. Lead is added to mercury, which can determine the properties of mercury. Sulfur, yellow in color, needs to be dry and non-wet to help the change of mercury.
Second, the utensils must be suitable. A must-have pill furnace is preferably burned with clay. The fireplace is thick and solid, and it can keep the heat even. The furnace cover is tightly sewn to prevent the escape of medicine gas. There are also pestles and sockets to finely study various medicines and make them fully mixed. When studying, the force needs to be even, and the powder of the medicine is as fine as dust.
Third, the control of the heat is the key. First preheat the pill furnace, and dry it slowly over a gentle fire to dry the furnace body. Then put the prepared medicine into the furnace, and simmer it slowly over a low heat at the beginning, so that the medicines can slowly blend. Seeing the change of the medicine, gradually turn to medium heat, and observe the change of its color and shape. At this time, the medicine is boiling in the furnace, and the agility of mercury fights with the medicines. Turn to martial fire at the right time, the fire is fierce, and the medicine is urged to speed up. However, the martial fire is not long, and the medicine is easy to get old after a long time. When the color of the medicine turns red, then adjust it to a gentle fire, and slowly raise it, so that the medicinal properties are mild.
Fourth When making medicines, it is necessary to be in a well-ventilated place. Because mercury is toxic, beware of poisoning. You need to be attentive when adding medicines and watching fires, and you must not slack off a little. If there is a difference, the pill will be difficult to make, or the drug-causing properties will be impure. According to these steps and with caution, it is expected to produce one percent of mercury and eighteen pills.

Those who hide eighteen insects should be cautious when storing and transporting them.
When storing, the first priority is the suitability of the environment. The nature of the insects is different, or they like dampness or dryness, so they must choose the place according to their nature. If it is in a damp and humid place, it is advisable to build a high platform to keep it away from the earth's atmosphere and prevent it from being damp and rotten; if it is a dry Gu, they need to choose a well-ventilated place to prevent it from being sultry and hot. And the storage place should be protected from the disturbance of humans and beasts, and barriers should be set up to prevent accidents.
When transporting, the method of wrapping is crucial. Wrap it layer by layer with silk first, so that it is tight so that there is no gap for the insects to escape. Then fill it with a wooden box, and fill the box with soft objects, such as cotton wool, hay, etc., to absorb shocks and prevent collisions, so as to avoid damage on the way. The person handling it must choose a stable and reliable one, and make it aware of the characteristics of the Gu, and be cautious. During transportation, choose a smooth road, and do not make the bumps too big. If you wade in water, you need to prevent the boat from shaking and the box from tipping over; if you take the land road, avoid the rough road, and move slowly and steadily.
In addition, both storage and transportation should always check the state of the Gu. Regularly check whether the package and wooden box are in good condition, and whether there is any abnormality in the movement of the Gu. If you see that the Gu is sluggish or the color changes, quickly check the reason, or adjust the environment, or apply rescue and treatment methods. In addition, the storage and transportation places should be prepared with first aid medicine and materials to prevent the accidental leakage of Gu poison and hurt people, and immediate rescue to protect both people and Gu. In this way, the essentials of storage and transportation can be avoided.