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"Tiangong Kaiwu" says: "Sheep are the main source of food and the resource of fur and brown." The functions of sheep are roughly two, one is for food and the other is for clothing.
Sheep are used as a way of eating, and have been an important source of meat for human beings since ancient times. Its meat tastes delicious and is rich in nutrition. According to the "Book of Rites and Nei-Rules", "six animals for food", sheep is one of them, which shows that it played an important role in the diet of the ancients. There are many ways to cook sheep, and it is excellent to cook, boil, and stew. For example, roast sheep, roast it with fire, the outer skin is burnt, the inside is tender, and the aroma is overflowing, which is mouthwatering. Boiled sheep soup is delicious and mellow, and drinking it in winter can warm the body and keep fit.
As for the use of clothing, wool and sheepskin are indispensable. Wool is soft and warm, and can be woven into felt blankets and fabrics to keep out the cold. Sheepskin is tough and thick, and it is made into fur clothing, which has excellent warm performance. The ancients often wore sheepskin fur clothing in cold winters to protect against the cold wind and snow. In ancient times, dignitaries preferred to use lamb skin to make fur, which was soft in texture and smooth in color, making it a symbol of status.
It is also the milk of sheep, which can also be eaten and is quite nutritious. Sheep manure can be used as fertilizer, nourishing the land and conducive to the growth of crops. Sheep are a treasure in the farming society, providing important support for many aspects of people's livelihood and occupying an indispensable position in the lives of the ancients.

Mercury, its nature is the most spiritual, and its quality is the most gentle. "Tiangong Kaiwu" has a saying: "Mercury, its substance is amorphous, shaped according to the object, round or square, and enters when it encounters a gap, such as the nature of a snake and scorpion."
Mercury is white as silver, and at room temperature, it is a liquid, flowing and shimmering. Its specific gravity is quite large, heavy and abnormal, and it is even more than that of ordinary things.
And mercury is toxic, which is one of its major characteristics. Although the ancients did not specify the depth of its toxicology, they knew that it should not be touched lightly. If you eat it by mistake, or inhale its vapor, it will cause damage to the viscera, chaos of qi and blood, and even endanger life.
In addition, mercury is also highly volatile. Placed in the air, it will soon dissipate without a trace, as if invisible. In a confined space, the vapor gradually accumulates, and the toxicity is even more severe, so the ancients also had many precautions.
The chemical activity of mercury is not weak, and it can combine with many metals to form amalgam. The properties of this amalgam are different from those of mercury and raw metals. The ancients often used this property to extract metals or make utensils.
The physical properties of mercury are truly unique. Its liquid shape, heavy quality, strong toxicity, evaporation speed, and strong activity are all significant characteristics of mercury, which are unique among all things in heaven and earth. The cognition and application of mercury by the ancients also left valuable experience and inspiration for the development of chemistry in later generations.

Lead and mercury are also the genus of hardware. Lead, blue and heavy in quality, has a sinking nature; mercury, white and flowing in quality, has a flexible nature.
The chemical properties of lead, with the common properties of metals, can conduct heat and transfer, and is relatively stable. However, in the air, it is oxidized for a long time, forming a layer of gray film to protect its interior. Lead and acids, such as dilute sulfuric acid and hydrochloric acid, react slowly; in case of nitric acid, it reacts quickly, producing lead nitrate and other substances.
Mercury, at room temperature, is a liquid metal and is the only liquid metal. Its surface tension is very large, so it often aggregates into beads. The chemical properties of mercury are also relatively stable, but it can be quickly combined with sulfur powder to produce mercury sulfide, which is one of its characteristics. Mercury and oxygen are heated to form mercury oxide.
Both lead and mercury are toxic. Lead enters the human body, and it is difficult to excrete it for a long time, harming the nervous, blood, digestive and other systems. Inhalation of mercury vapor also damages the human body, especially the nervous system.
The chemical properties of lead and mercury are different. Lead is heavy and heavy, but mercury flows and lives. When lead is oxidized, a film is formed, and mercury and sulfur combine and melt quickly. Although the two are metals, their properties are different. The world should use it with caution, so as to prevent its poison from causing harm to the world.

In the method of "Tiangong Kaiwu", the method of making realgar from arsenic stone is quite delicate. The method first takes arsenic stone, selects the pure quality without impurities, and calcines it with charcoal fire. In a special crucible, seal it tightly and do not let it deflate. When calcining, the fire needs to be uniform and fierce, and when the arsenic stone melts into a liquid, it looks like flowing gold.
Then, prepare turpentine, which needs to be collected from age-old pine, and its nature is pure and thick. The turpentine is gradually thrown into the pickled liquid, and the throwing is slow, and the bamboo chopsticks are stirred quickly to make the two blend. At this time, it can be seen that the smoke in the pot is evaporating, the color is slightly yellow, and the odor is mixed with pungent gas.
After a while, cease fire, and wait for it to cool. The speed of cooling is also exquisite. If it is too fast, the quality will be uneven, and if it is too slow, it will take time. When it condenses into blocks, it can be smashed, and there may be slightly yellow like gold grains in it, which is the newly formed realgar.
However, this is only a preliminary production. If you want to get pure realgar, you need to refine it. Wash it with water, remove its dross, and then slightly bake it with charcoal fire. When baking, turn it frequently to make it dry and wet. Repeat this several times until the color is pure yellow and the quality is uniform, and it is the top-grade realgar.
The method of making realgar depends on the heat, the proportion of materials used, and the fineness of the operation. If the heat is too strong, the arsenic will evaporate and not exist, and if it is too weak, it will be difficult to blend with turpentine; if the proportion of materials used is improper, the realgar is impure; if the operation is not careful, it may cause accidents. This requires many years of experience by craftsmen to be handy and make good quality realgar.

Mercury, during storage and transportation, many matters should be carefully paid attention to.
Mercury has special properties, is liquid at room temperature, and is volatile, and its vapor is highly toxic. Therefore, when storing, choose the first heavy container. It is advisable to use a thick and airtight metal container, such as a tin can, to prevent the leakage and volatilization of mercury liquid. If you hold it in an ordinary container, if you are not careful, the mercury will escape and cause harm to the surroundings. And the container should be placed in a cool, dry and well-ventilated place to avoid heat and moisture. Heat will increase the volatilization of mercury, and moisture will easily cause the container to rust and damage its airtightness.
During transportation, stability is essential. The mercury liquid should be properly fixed to prevent it from swaying in the container and causing damage to the container. Handling must be gentle and must not be bumped and collided. Furthermore, the transportation environment should also be carefully inspected. The temperature should not be too high. If it is too high, the mercury will evaporate rapidly. Escorts must be familiar with the hazards of mercury and emergency disposal methods. If there is a leakage of mercury liquid, evacuate the crowd immediately and block the source of fire, because its steam is flammable. And quickly cover the leakage with sulfur powder. Mercury and sulfur can be synthesized into mercury sulfide, which is greatly reduced in toxicity, and then properly cleaned up.
In addition, the storage and transportation of mercury must be strictly followed by relevant laws and regulations. From container standards to transportation qualifications, there are clear regulations. Don't take chances and act illegally. If there is a slight mistake, the harm of mercury will spread, causing catastrophe to human health and the surrounding environment. It is necessary to be cautious in everything to ensure safety.