Acide 4-bromopyridine-3-carboxylique

Borax is a common mineral with unique chemical properties. Borax, whose main component is sodium tetraborate, often appears as colorless translucent crystals or white crystalline powder.
Borax has many chemical properties. First, its aqueous solution is alkaline. Because borax hydrolyzes in water, borate ions combine with hydrogen ions ionized by water, which increases the concentration of hydroxide ions in the solution, so it appears alkaline. For example, although the alkalinity of borax is not specifically recorded in Tiangong Kaiwu, in traditional processes, alkaline substances often play a role in specific processes, or the alkalinity of borax can be deduced to some ancient processes or potential applications.
Second, borax has buffering properties. To a certain extent, it can maintain the stability of the pH of the solution. Even if a small amount of acid or alkali is added, the pH value of the solution does not change much. This property is of great significance in the fields of chemical industry and medicine. Although there is no modern precise chemical theory in ancient times, in long-term practice and exploration, this property of borax may be applied, such as in some processes such as brewing and dyeing that need to stabilize the pH.
Third, borax can react with a variety of metal ions to form complexes with specific colors or properties. If it reacts with copper ions, it can form complexes with characteristic colors, which can be used to identify or separate metal ions. In ancient metallurgy, alchemy and other activities, borax may have been used to purify or treat metals.
Fourth, borax will undergo changes such as dehydration when heated. With the increase of temperature, the crystal water is gradually lost, the crystal structure changes, and the appearance also changes. This feature may have applications in ancient firing ceramics, glass and other processes, or it can help adjust the melting point of raw materials and improve the properties of products.

To make boric acid and borax, there are various ancient methods. First, the boron-magnesium ore is co-heated with sulfuric acid. Boron-magnesium ore, magnesium borate-containing ore is also. Mix the boron-magnesium ore powder with sulfuric acid in an appropriate proportion, put it in a kettle, and heat it. The reaction formula is: $Mg_2B_2O_5 · H_2O + 2H_2SO_4\ stackrel {\ Delta }{=\!=\!=} 2MgSO_4 + 2H_3BO_3 $. After the reaction is completed, the impurities such as calcium sulfate are filtered out, and then concentrated and crystallized to obtain boric acid. The remaining mother liquor, if reprocessed, can be obtained Borax.
Second, borax is reacted with sulfuric acid. Borax, that is, sodium tetraborate ($Na_2B_4O_7 · 10H_2O $). Take the solution of borax, slowly drop sulfuric acid into it, and properly control its acidity. The reaction is as follows: $Na_2B_4O_7 + H_2SO_4 + 5H_2O\ stackrel {}{=\!=\!=} Na_2SO_4 + 4H_3BO_3 $. After the reaction, boric acid can also be obtained after separation and purification. The sodium sulfate produced by the reaction, if separated from boric acid, is treated with an appropriate amount of boric acid and other materials according to a specific method, or borax can be produced.
There is also a method of co-melting boron ore with soda ash. Choose a suitable boron ore, mix it with soda ash, and melt it in a high temperature furnace. After the reaction, a melt containing sodium borate is obtained. The frit is leached in water, filtered to remove impurities, and then adjusted to its pH value with acid to precipitate boron in the state of boric acid. If the boron-containing solution is further processed and the conditions are controlled, borax can also be prepared. These methods have their own advantages and disadvantages, and need to be selected according to the availability of raw materials, cost considerations, product purity and other factors.

Mercury is a highly toxic substance, and its nature is strong and harmful. Arsenic is also a toxic substance, and both have their own special characteristics in many fields. Here is the way for you.
Mercury, in the medical way, has occasionally been used as a medicine in the past, but because of its severe toxicity, it is rarely used today. In ancient times, there were doctors who wanted to use it to attack poison, kill insects, or treat scabies and sores. However, if they used it carelessly, they would not cause harm, causing damage to the patient's internal organs and corruption of qi and blood.
In the art of alchemy, mercury is also the key thing. Ancient alchemists tried to use mercury and other substances to refine the elixir of immortality, thinking that they could be turned into immortals. However, mercury is refined by fire, and its toxicity is even more severe. Those who take pills are often poisoned to death, such as the emperors of the Tang Dynasty. There are many people who die from illness due to taking pills.
As for the field of metallurgy, mercury can be used to extract precious metals such as gold and silver. However, in this process, mercury gas escapes, causing harm to the shallow, and those who work are prone to mercury poisoning, causing tremors in the limbs, trance and other diseases.
Arsenic, in agriculture, used to use it to make pesticides to remove pests in the past. However, it remains in the soil and crops, and when eaten by humans, it is poisoned in the body, damaging the viscera and meridians.
It has also been used in medicine in the past, such as to treat malaria and ulcers, etc. However, the dosage is extremely difficult to control, and it will be poisonous after a while.
And in the chemical industry, arsenic and its compounds may be used in the production of pigments, glass, etc. However, if the production process is not handled properly, arsenic will pollute the environment and endanger all living beings.
In short, although mercury and arsenic have their applications in the past or in some specific fields, they are used cautiously today because of their severe toxicity, in order to prevent it from causing harm to the world and causing endless consequences.

In today's world, the price of salt and sugar in the market is related to people's livelihood, and it also involves various reasons.
Salt is a necessity for people's livelihood, and it is an important thing for the country to manage. Throughout the ages, salt has been strictly controlled, and its price has not changed arbitrarily. The court considered the livelihood of the people, so it often controlled the price of salt in a stable environment. And salt comes from a wide range of sources, either from the sea, or from wells, or from mines, and the supply is constant. Therefore, the market price of salt, even if there is a small movement, is generally maintained within a reasonable range.
Sugar, one of the things, has a variety of reasons for its price change. First, it concerns raw materials. Sugar is mostly derived from sugar cane, beets and the like. If the weather is smooth and the raw materials are abundant, the production of sugar will increase, and the price may stabilize and decline; in case of famine, the raw materials will not be harvested, and the price of sugar will rise. Second, it involves manufacturing. The production of sugar requires manpower and material resources. If the manufacturing method advances, the cost will decrease, and the price may also fall; if the labor cost increases, the price will rise. Third, it depends on supply and demand. If there are many sugar seekers in the market, and the supply is small, the price will be high; if the supply exceeds the demand, the price will be low.
Looking at the city today, the price of salt is stable but rarely changes to ensure the basic needs of the people. The price of sugar fluctuates from time to time due to various reasons. However, they are all in the midst of market regulation and imperial court regulation to achieve a balance between supply and demand and ensure the safety of people's livelihood. Although there are fluctuations from time to time, they are all normal conditions in the market and common sense in economic operation.

Borax is a compound of boron, and its physical properties can be investigated.
First of all, its appearance, borax is often colorless and translucent crystal shape, or white powder, like the white of frost and snow, transparent like the radiance of ice. Its shape is regular, the crystal surface is smooth and shiny, and it refracts and shines under light, just like a pearl containing light.
Times and hardness, borax hardness is quite low, and it leaves traces when scratched with a fingernail. The texture is soft and not rigid.
Furthermore, in terms of its solubility, borax is easily soluble in water, and the higher the water temperature, the faster it dissolves. Just like ice and snow meet the warm sun and melt into the invisible. The borax is placed in water, with a little stirring, it gradually melts into the water body and forms a uniform solution.
In addition to its density, compared with many common minerals, the density of borax is moderate, and it feels heavy in the hand, but it is not like the heavy pressure of gold and stone.
The melting point of borax is not very high, and it is easy to melt into a liquid when heated, just like a wax torch heated, and the shape changes from solid to liquid, showing a different state.
Borax can slowly weathering in the air, like a beauty that has been worn out over time, losing its original moist, and gradually changing slightly. This is the physical properties of borax, which is used in many fields such as industry, medicine, and scientific research. With this characteristic, each has its own capabilities, and it is widely used and indispensable.