Therefore, the failure of Jianzhen's previous few failures in the east does not mean that the Tang Dynasty's navigation and shipbuilding technology are backward. His eastward ferry is prohibited by the government, and failure is normal for the same behavior as smuggling.

Both Li and Zhang Chong knew about these things, but one thing Li once said was that it was precisely the reason why the Westerners drifted near Japan and the reason why the Tang Dynasty's navy could not sail too far. That is, the Tang Dynasty's shipbuilding technology is indeed good now, but there is another thing that cannot be done, that is, there is no chart.

Navigation, as the name suggests, is a navigation map. Because the sea navigation industry of the Tang Dynasty has been idle for so long in recent years, the navigation has long since expired. Zhang Chong has been constantly sailing on the sea in recent years, and has been improving the navigation around the Tang Dynasty and Japan. However, for no reason, he cannot be so risky.

Another very important question is that there is no accurate compass appearing at this time.

Li Qing was indeed a figure who had been tombs in his previous life, but he really didn't understand science, so he couldn't solve this problem. He also found many craftsmen in Chang'an City, but it was really difficult to accomplish now to invent the kind of compass with very high precision.

And there is another thing, in fact, Li Qing didn't tell them, that is, he had been organizing some personnel to refine a secret weapon near Chang'an City, that is gunpowder.

Moreover, gunpowder was discovered through alchemy, and normally it was discovered through failed alchemy, so Li Qing knew that in this era, he was still very likely to tinker with gunpowder. If gunpowder came out, many things would be much simpler.

Alchemy originated very early, and there are records in "The Strategies of the Warring States" that alchemists offered immortal medicine to King Jing. Emperor Wu of Han also wanted to "live forever" and asked the people for elixirs, recruit alchemists, and refine alchemists himself. From then on, alchemists became popular and began to become popular. Alchemists have appeared throughout the ages, which are the so-called alchemists. The purpose of alchemists was to find the medicine for immortality, which was impossible to achieve. Alchemists were popular for more than a thousand years, but in the end they still found nothing. However, some specific methods used in alchemism are still worthy, and they show the original form of chemistry.

A very important method in alchemy is "fire alchemy". It is directly related to the invention of gunpowder. The so-called "fire alchemy" is probably an unwater-free heating method. Ge Hong of the Jin Dynasty recorded the fire method in "Baopuzi". The fire method generally includes: calcination (long-term high-temperature heating), refining (heating of dry matter), moxibustion (local baking), melting (melting), pumping (distillation), flying (also known as as ascending, sublimation), and excrement (heating) (heating) and excrement (heating) to denaturate substances). These methods are the most basic chemical methods, which is also the basis for the ignorant profession of alchemy to produce inventions. The piety of alchemists and the frustration of finding immortal medicines have forced alchemists to repeatedly experiment and find new methods. This creates conditions for the invention of gunpowder. Before the invention of gunpowder, alchemism had obtained some artificial chemicals, such as mercury sulfide, etc. This may be one of the earliest products made by chemical synthesis.

Although alchemists have mastered certain chemical methods, their direction is to seek immortality, so the invention of gunpowder is somewhat accidental.

Alchemists often use burning methods to "suppress" the drugs that are poisonous, such as sulfur and arsenic, before using them, and "suppress" means subduing. The toxicity is lost or reduced. This procedure is called "Fuhuo". Sun Simiao, a famous doctor and alchemist in the early Tang Dynasty, recorded in the "Sulphur Method of Endosus Viagra": grind two taels of sulfur and saltpeter into powder, and put them in a silver pot or sand pot. Dig a pit, put the pot in the pit and the ground, and fill it with soil on all sides. Three soaps that have not been eaten by insects are scrambled into one point, then put them into the pot, and fire the sulfur and saltpeter. When the fireworks cannot be burned, they will fry them with charcoal. After the charcoal is eliminated by one-third of the charcoal, anneale, and before cooling, take the mixture, and then put it in.

In the middle of the Tang Dynasty, a man named Qingxuzi proposed a prescription for fuhuo in the "Fuhuo Alum Method": "Two liang of sulfur, two liang of nitrogen, and three and a half cents of Aristolochia. The right is powdered, mix well, dig a pit, put medicine in the pot and level with the ground. Put a piece of cooked fire together, and put it in the pine, put it in the inside, and the smoke gradually rises." He used Aristolochia instead of the soap beans in Sun Simiao's prescription, and these two substances replace carbon to burn.

The prescriptions for Fuhuo all contain carbon, and saltpeter should be added to sulfide, and saltpeter should be added to sulfide. This shows that alchemists intend to cause the drugs to burn to remove their poison.

Although alchemists know that mixed ignition of sulfur, nitrate and carbon will cause intense reactions and take measures to control the reaction speed, accidents caused by drug fires often occur. There is a story in "Taiping Guangji" that tells that in the early years of the Sui Dynasty, a man named Du Chunzi visited an elderly alchemist.

Living there that night. Du Chunzi woke up in a dream in the middle of the night and saw "purple smoke penetrated the house" in the alchemy furnace, and the house immediately started to burn. This may be because the alchemist negligently configured flammable drugs and caused a fire.

There is also an alchemy book called "The Essential and Wonderful Dao" that also talks about the use of sulfur, saltpeter, realgar and honey to make a fire. The torch burns people's face and hands, and it also hits the roof and burns the house. The book tells the alchemists to prevent such accidents from happening.

This shows that the alchemists in the Tang Dynasty have mastered a very important experience, that is, sulfur, nitrate and carbon can form a very flammable medicine. This medicine is called "ignition medicine", that is, gunpowder. Since the invention of gunpowder came from the process of making pills and making medicines, it was used as a medicine after the invention of gunpowder. In the "Compendium of Materia Medica", it is mentioned that gunpowder can cure sores, kill insects, ward off moisture, and plagues.

Gunpowder cannot solve the problem of immortality and is prone to fire, so the alchemist is not interested in him. When the alchemist's formula was transferred from the alchemist to the military strategist, it became black gunpowder, one of the four great inventions in ancient China.
Chapter completed!