Soap in the Song Dynasty, a kind of synthetic detergent appeared. It is to crush and grind the natural Saponaria pods (also known as Saponaria, dangdao, soap pods, commonly known as Saponaria), add spices and other things, and make them into orange-sized balls, which are specially used for washing face and bathing body, commonly known as “soap dough”. Song people carefully recorded that Lin’an, the capital of the Southern Song Dynasty, had a businessman who specialized in “soap Troupe” in Volume 6 of the old story of Wulin. In compendium of Materia Medica written by Li Shizhen of Ming Dynasty, the manufacturing method of “soap dough” is recorded: soap pods grow in high mountains, trees are tall, leaves are like sandalwood and soap pods, flowers in May and June, pods are 34 inches, plump and fleshy, there are several sunspots inside, big as fingers, not round, white kernel in them, edible. It’s better to pick pods in October, boil them and mash them, and make pills with white flour and various fragrances. It’s better to take a bath and get rid of dirt and greasiness. In addition to the natural Acacia, such as the disease-free seed and other plants, also spread in the folk, become a good detergent. In the west, it can be traced back to an ancient Greek island called lepos 4000 years ago. The local people sacrifice animals to heaven. Because they burn animals with wood, the ashes of wood and animal fat mix to produce a soap-like yellow substance. The heavy rain washed these things into the river where local women often wash clothes, and they found that the clothes were cleaner. Although traces of the use of soap have been found since ancient Greece, there is a female poet named Sappho (saponification) who recorded these stories in history. Later people called this process saponification in memory of her. The chemical name was soap making. In addition, in 3000 B.C., Mesopotamians found that the alkaline substances of ashes after burning plants mixed with oil have the ability of decontamination, which is also one of the sources of soap. However, Gauls should be the first successful people to try to make soap. They called soap “SAPO” at that time, which was a kind of ointment containing animal oil and plant ashes. When SAPO was gradually introduced into the Mediterranean region, the Arabs improved SAPO into olive oil and solid soap made of soda. At this point, soap began to be manufactured in large quantities. And it was in the 18th and 19th centuries that soap was really popular. After the industrial revolution industry came out in the late 18th century, a large number of cheap sodium carbonate was obtained, which promoted the development of the soap industry. However, by the middle of the 20th century, the development of synthetic chemistry and the petrochemical industry provided cheap chemical raw materials for detergents, promoted the rise of synthetic detergents, and made great changes in the development of the soap industry. However, in recent years, the rise of hand-made soaps, whose environmental awareness has been ignored, has been on the rise again. Due to its unique natural performance, various components are easily biodegradable and It is easy to be decomposed by microorganisms in the sewage treatment process, so it will not cause pollution problems of rivers, lakes, and waterways.