What is the essential difference between soap and detergent?

Soap Soap is an indispensable daily washing product, and the history of people using soap can be traced back to Italy before BC. Soap has been widely used in China since 1980s. As one of the most common and widely used personal washing products, soap has its own advantages and disadvantages. First of all, the main component of soap is sodium fatty acid, which is basically saponified from oil (vegetable oil or animal oil), which has no toxic and side effects on human body and is easily degraded by the environment; Therefore, it can be said that soap is a "natural" green product. In fact, fatty acids and their derivatives are the most widely used raw materials in cosmetics. However, because sodium fatty acid is alkaline (PH value is about 10) and the skin surface is weakly acidic (PH value is about 6.5), the PH value of the skin surface will be greatly increased after washing with soap, which will cause certain allergic phenomena to highly allergic skin, and at the same time, it will wash off the lipid layer on the skin surface and make the skin dry. Due to the elasticity of the skin itself, the original PH value of the skin surface will be restored within 15-30 minutes after washing. Soap According to historical records, the earliest soap formula originated in Mesopotamia, West Asia. About 3000 BC, people mixed 1 part oil and 5 parts alkaline plant ash to make a detergent. There are many legends about the origin of soap in Europe. Speaking of Gauls in ancient Rome, sheep oil and beech ash solution were stirred into a thick shape every holiday, coated on hair and combed into various hairstyles. Once a festival was caught in heavy rain, and the hairstyle was ruined, but people unexpectedly found that the hair became clean. It is also said that when the Romans sacrificed to the gods, the fat of roasted cattle and sheep dripped into the plant ash, forming a "grease ball". When women wash clothes, they find that clothes stained with "oil balls" are easier to clean. This shows that people have used animal fat and plant ash soap for thousands of years. Archaeologists discovered a soap-making workshop in the ruins of Pompeii, Italy. This shows that the Romans had already started the primitive soap production as early as the 2nd century AD. China people have long known that plant ash and trona are used for washing clothes. People also mix pig pancreas and lard with natural pork to make a lump called "pancreas". Early soap was a luxury. Until 179 1, French chemist Lublan successfully made caustic soda from electrolytic salt at a low price, thus ending the ancient method of making caustic soda from plant ash. 1823, German chemist Cheever discovered the structure and characteristics of fatty acids, and soap is one of them. At the end of 19, the soap-making industry changed from manual workshop to industrial production. Soap can decontaminate because it has a special molecular structure. One end of the molecule is hydrophilic and the other end is lipophilic. At the interface between water and oil, soap emulsifies oil and dissolves oil in soapy water. At the interface between water and air, soap surrounds air molecules to form soap bubbles. The dirt that was originally insoluble in water can no longer adhere to the surface of clothes because of the action of soap, but is dissolved in soap foam and finally washed away completely. /kloc-in the 0/8th century, the French made "artificial soda" from salt and Carboniferous to replace the traditional alkali juice extracted from ashes. /kloc-in the 0 th and 9 th centuries, the Germans invented sodium hydride by electrolyzing salt water; Since then, the popularity of caustic soda has changed soap from a commodity that only the nobles in the palace can afford to a daily necessities for ordinary people. Before that, the manufacture of soap depended on experienced craftsmen. It is prepared with oil-alkali ratio juice, because there is no information to refer to, and it is often tried again because it cannot be solidified. It is worth mentioning that in the United States during the pioneer period, immigrants would choose warm days in early spring and gather the whole village to make soap. The material source of soap is the astringent juice extracted from oak, beech and other wood as the source of alkali juice. If it is not enough, supplement it from the ashes of the heater. With alkaline juice, we can get oil from animal fat or vegetable oil for cooking, but once the oil and water are separated, we have to start all over again. Only in the19th century did enterprises invest in the production of soap. When people wash their hands with antibacterial soap, they are exposed to low doses of antibacterial agents. After long-term contact, drug-resistant strains are easy to produce, and sometimes even grow and reproduce, which is harmful to human health. Washing hands frequently in daily life, whether using antibacterial soap or not, can also reduce the chance of mouth-to-mouth disease. "As long as you use ordinary fat (fragrant) soap and wash it with running water, you can wash off 80% to 90% of the bacteria on your skin. In order to protect the health of your family, it doesn't matter whether you use antibacterial soap or not. "

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