How was gunpowder invented?

The invention of gunpowder obviously began with the discovery and research of deflagration. In order to prevent the deflagration disaster in the process of alchemy, the alchemists in the early Tang Dynasty fully realized that saltpeter, sulfur and realgar were all substances that caused deflagration, and the key substance was saltpeter. Therefore, they studied its fire extinguishing method and tested its combustion-supporting technology, and obtained the method to control the reaction of nitrate, sulfur and carbon. The warnings about burning saltpeter and sulfur in the works of then, as well as the deflagration caused by the use of saltpeter and sulfur, such as Zhenyuan Miao Road Yao, the method of alchemy of different factions, the fusion of lead, mercury, Jia Geng and Bao, all indicate that alchemists had mastered the formula of gunpowder in the middle Tang Dynasty. However, only when the formula of gunpowder is really applied to production and life, first of all, the invention of gunpowder can be truly completed. In ancient times, it often took a long cognitive process from the discovery of a natural phenomenon to the conscious use of it. The invention of gunpowder also had this cognitive process. From the discovery and research of deflagration of elixir to the understanding and mastery of gunpowder formula; From the means of preventing deflagration to the military application of deflagration, it is indeed a process of practical understanding.