Soap is a general term for fatty acid metal salts. The general formula is RCOOM, where RCOO is a fatty acid radical and M is a metal ion. The carbon number of fatty acids in daily soap is generally 10-18, and the metals are mainly alkali metals such as sodium or potassium. Special purpose soap can also be made from ammonia and certain organic bases such as ethanolamine and triethanolamine. In a broad sense, fatty acid salts obtained by saponification or neutralization reactions between oils, waxes, rosin, or fatty acids and alkalis can all be called soap. Soap can dissolve in water and has a washing and cleaning effect. There are various types of soap, including soap, also known as wash soap, metal soap, and composite soap.
Soap is a general term for fatty acid metal salts. The carbon number of fatty acids in daily soap is generally 10-18, and the metals are mainly alkali metals such as sodium or potassium. Special purpose soap can also be made from ammonia and certain organic bases such as ethanolamine and triethanolamine. Soap includes laundry soap, soap, metal soap, liquid soap, as well as related products such as fatty acids, hardening oil, glycerin, etc.
Ingredients of soap: Sodium salt of carboxylic acid R-CO2Na, synthetic pigments, synthetic fragrances, preservatives, antioxidants, foaming agents, hardeners, thickeners, synthetic surfactants.
The main component of soap is R-CO2Na (sodium stearate (C17H35COONa)), where the R group is generally different and consists of various alkyl groups. R - is hydrophobic, carboxyl is hydrophilic. In hard water, soap forms curd like substances and fatty acid calcium salts with Ca2+, Mg2+, etc., commonly known as "calcium soap", which becomes a useless descaling agent. Adding a softener to hard water can remove hard water ions and make soap effective. Medicinal soap mainly contains some disinfectants added to it. Soap is added with essence. Soap has strong degreasing power due to its soap alkali content.
When ancient people were in the Yellow River Basin, they used soapberry to wash clothes, but later on, there were no soapberry trees in the Yangtze River Basin. Later, they discovered another tree whose fruit had the same properties as soapberry pods and could wash clothes, but was thicker and fuller than soapberry pods. Therefore, they named it soapberry or soapberry.
When artificial detergents were invented later, the word 'soap' was still used.
So, although there is no slimming soap, there is a non fat soap called 'soapberry'.
Soap was made and introduced from the West, so it was called "sodium carbonate" at that time. Although "sodium carbonate" and soap itself could not be equated, the Chinese people, driven by novelty, still used the name officially for decades, until the national industry and commerce made their own fat soap, and then gradually abandoned the word "foreign".
In ancient times, whether in the East or the West, the earliest washing ingredients were nothing more than sodium carbonate and potassium carbonate. The former is a natural lake mineral product, while the latter is the main washing component of plant ash. The invention of soap is said to have been by the Phoenicians on the eastern coast of the Mediterranean. Legend has it that in a palace in ancient Egypt in the 7th century BC, a Phoenician chef accidentally spilled a jar of cooking oil on the ground. He was very scared and quickly used the ashes from the stove to sprinkle on it before anyone else noticed. Then he picked up the mixture of oil soaked ashes and threw them away with his hands.
Looking at the grease on his hands, he thought to himself: With such dirty hands, I don't know how long it will take to wash them clean! He hesitated while putting his hand into the water. A miracle occurred: he just gently rubbed a few times, and the greasy residue on his hands was easily washed off. Even the old dirt that was previously difficult to wash off has been washed away. This chef is very strange, so he asked other chefs to try using this grey oil, and everyone's hands were washed cleaner than before. So the servants in the kitchen often wash their hands by mixing oil with wood ash. Later, the Pharaoh also learned of this secret and asked the chef to make some wood ash mixed with oil for him to wash his hands with.
Of course, legends are just legends and may not be entirely taken seriously. However, the Egyptian Lake near Alexandria is rich in natural sodium carbonate, so the washing technology in ancient Egypt was relatively advanced, and it is not surprising that soap was invented.
Soap is a general term for fatty acid metal salts. The carbon number of fatty acids in daily soap is generally 10-18, and the metals are mainly alkali metals such as sodium or potassium. Special purpose soap can also be made from ammonia and certain organic bases such as ethanolamine and triethanolamine. Soap includes laundry soap, soap, metal soap, liquid soap, as well as related products such as fatty acids, hardening oil, glycerin, etc.
In addition to high fatty acid salts, soap also contains rosin, water glass, spices, dyes and other fillers. Structurally, the molecules of sodium higher fatty acids contain non-polar hydrophobic moieties (alkyl groups) and polar hydrophilic moieties (carboxyl groups). Hydrophobic groups have lipophilic properties. During washing, the grease in the dirt is stirred and dispersed into small oil droplets. After coming into contact with soap, the hydrophobic group (alkyl group) of sodium higher fatty acid molecules inserts into the oil droplets and binds with the grease molecules through van der Waals forces. And the hydrophilic group (carboxyl group) that is easily soluble in water extends outside the oil droplet and inserts into the water.
In this way, the oil droplets are surrounded by soap molecules, dispersed and suspended in water to form an emulsion, which is then rinsed away with water through friction and vibration. This is the principle of soap stain removal. However, regular soap should not be used in hard or acidic water. Due to the formation of insoluble calcium and magnesium salts in hard water, and insoluble fatty acids in acidic water, their ability to remove dirt is greatly reduced.
According to historical records, the earliest soap recipe originated in Mesopotamia, West Asia (meaning "the place between two rivers", referring to the area between the Euphrates and Tigris rivers). Around 3000 BC, people mixed 1 part oil and 5 parts alkaline plant ash to make a cleaning agent. There are many legends about the origin of soap in Europe. It is said that the Gauls of ancient Rome would mix sheep oil and beech ash solution into a thick consistency during festivals, apply it to their hair, and comb it into various hairstyles. Once, during a festival, there was a sudden heavy rain that damaged my hairstyle, but people unexpectedly found that their hair had become clean. Legend has it that when the Romans offered sacrifices to their gods, grilled beef and mutton oil dripped into the ashes of plants and trees, forming "oil balls". Women find that clothes stained with "grease balls" are easier to clean when washing clothes. This indicates that people have been using animal fat and grass ash (alkali) soap for thousands of years.
Archaeologists have discovered a soap making workshop in the ruins of Pompeii, Italy. This indicates that the Romans had already started primitive soap production as early as the 2nd century AD. The Chinese have long known to use plant ash and natural alkali to wash clothes. People also mix pig pancreas and lard with natural alkali to make a piece, called "pancreas".
Early soap was a luxury until 1791, when French chemist Leland successfully produced caustic soda by electrolyzing salt at a low cost, putting an end to the ancient method of producing alkali from plant ash. In 1823, German chemist Schafer discovered the structure and properties of fatty acids, and soap is one of them. At the end of the 19th century, the soap making industry transformed from manual workshops to industrial production.
The reason why soap can remove dirt is because it has a special molecular structure, with one end of the molecule being hydrophilic and the other end being lipophilic. At the interface between water and oil, soap emulsifies the oil, allowing it to dissolve in soap water; At the interface between water and air, soap surrounds air molecules to form soap foam. The dirt that was originally insoluble in water can no longer be attached to the surface of clothes due to the role of soap, but dissolves in the soap foam, and is finally cleaned away.
In the 18th century, the French used salt and charcoal to make "artificial soda", replacing the traditional alkaline juice taken from ashes. In the 19th century, the Germans invented to produce sodium hydroxide by electrical decomposition of salt water; Since then, the popularity of caustic soda has enabled soap to transform from a commodity that was originally only affordable for palace nobles into a daily necessity for ordinary people.
Prior to this, soap manufacturing relied on experienced craftsmen. Using the ratio of oil and alkali juice to prepare, but due to the lack of available information, it is often re tried due to inability to solidify.
It is worth mentioning that in the pioneering era of America, immigrants would choose a day in early spring when the weather was warm and gather the whole village to make soap.
The material source of soap is extracted from oak, beech and other woods as astringent juice, which is used as a source of alkali juice. If it is not enough, it is added from the ashes of the heater. With alkaline juice, oil can be obtained from animal fat or vegetable oils used in cooking, but once the oil and water are separated, it is necessary to start over. It was not until the 19th century that companies invested in the production of soap.
The molecular structure of soap can be divided into two parts. One end is a charged polar COO - (hydrophilic site), and the other end is a non-polar carbon chain (lipophilic site). Soap can break the surface tension of water. When soap molecules enter the water, the polar hydrophilic parts will break the attraction between water molecules and reduce the surface tension of water, allowing water molecules to be evenly distributed on the surface of clothes or skin to be washed. The lipophilic parts of soap penetrate deep into oil stains, while the hydrophilic parts dissolve in water. This combination forms smaller oil droplets after stirring, and their surfaces are covered with the hydrophilic parts of soap, without re aggregating into large oil stains. This process (also known as emulsification) is repeated multiple times, and all oil stains will turn into very small oil droplets that dissolve in water and can be easily washed clean.
The main component is sodium stearate, with a molecular formula of C17H35COONa (carbon-17H25+carbon+oxygen+oxygen+sodium) (also written as RCOONa, produced by the reaction of sodium hydroxide [NaOH] with alkaline oils and fats). If spices and dyes are added inside, a soap with both color and fragrance will be made; If you add some medicine (such as boric acid or carbolic acid) inside, it will turn into a medicinal soap.
Soap was a synthetic detergent that appeared during the Song Dynasty. It was made by crushing and grinding natural soapberry pods (also known as soapberry, hanging knife, or soapberry pods, commonly known as soapberry), adding spices and other ingredients, and making them into orange sized balls specifically for facial cleansing and body bathing, commonly known as "soap balls". The Song Dynasty's "Wulin Old Stories" Volume 6 "Small Brokerage" records that there were already merchants specializing in running "soap operas" in Lin'an, the capital of the Southern Song Dynasty. The Ming Dynasty scholar Li Shizhen recorded the method of making "soap balls" in his "Compendium of Materia Medica": soap pods grow in high mountains, with tall trees and leaves like sandalwood and soap pods. They bloom in May and June, produce pods of three to four inches, are thick and fleshy, have several black spots inside, are as big as fingers, not perfectly round, and contain white kernels that are edible. Picking pods in October, cooking and pounding them, making pills with white flour and various fragrances, bathing the body, removing dirt and making them greasy, better than soapberry pods. In addition to natural soapberry pods, plants such as soapberry have also been passed down among the people and become a good detergent. In the West, it may be traced back to a small island called Lesbos in ancient Greece 4000 years ago. The locals use animals to offer sacrifices to the heavens. Due to the use of wood when burning animals, the ash from the 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 as a result, their clothes were washed cleaner. Although traces of soap like use can be found since ancient Greece, there is a historical record of a female poet named Sappho who recorded these stories. Later people, in commemoration of her, called this process saponification, and the chemical name was Soap Making. In addition, in 3000 BC, the Mesopotamians discovered that alkaline substances such as ashes from plant combustion, when mixed with oil, had cleaning power, which was also one of the sources of soap. However, the Gauls were probably the first to attempt and succeed in making soap, which they called "sapo" at the time. At that time, soap was an ointment like substance made by mixing animal fats and plant ashes. As the production techniques of sapo gradually spread to the Mediterranean region, Arabs improved sapo into hard soap made from olive oil and soda. At this point, soap began to be mass-produced. The true widespread use of soap dates back to the 18th and 19th centuries. After the industrial revolution emerged in the late 18th century, a large amount of inexpensive sodium carbonate was obtained, which led to new developments in the soap industry. However, in the mid-20th century, the development of synthetic chemistry and petrochemicals provided cheap chemical raw materials for detergents, promoting the rise of synthetic detergents and causing significant changes in the development of the soap industry. However, in recent years, the rise of environmental awareness has led to the emergence of handmade soap, which has been overlooked. Due to its natural and unique properties, handmade soap has various components that are easily biodegradable and easily decomposed by microorganisms in sewage treatment processes, so it will not cause pollution problems in rivers, lakes, and waterways.
refine
Remove impurities from the oil. The commonly used refining processes include de waxing, alkali refining (de acidification), and decolorization. Degumming is a hydration method that removes phospholipids and other colloids from oils and fats, using water to hydrate phospholipids and other colloids, and then precipitating them; The acid refining method of carbonizing and precipitating phospholipids and similar impurities using concentrated sulfuric acid. The main function of alkaline refining is to remove free fatty acids from oils and fats, but due to the generation of flocculent soap, it adsorbs and removes pigments and impurities from oils and fats.
saponification
After oil refining, it undergoes saponification reaction with alkali. Boiling method is the main saponification method, and the soap pot is cylindrical or square in shape.
In addition to the pipelines for transporting oil, alkali solution, water, salt water, etc., there are also direct steam or steam coils installed to introduce steam and stir the soap material evenly. There is also a shaking tube in the pot, and the upper opening of the tube can be placed at any liquid level to discharge the soap material in the pot. The bottom of the pot is conical, and there is a feeding tube underneath to release the residual liquid left after the shaking tube is discharged. Boil the oil and caustic soda in a soap pot until the saponification rate reaches about 95%, and stop the saponification operation when the soap material is in a uniform closed state.
Salting out
Add salt or saturated saline solution to the closed soap material to separate the soap from the diluted sweet oil. The minimum concentration that causes soap to precipitate is called the salt precipitation limit concentration. After the closed soap gel undergoes salt precipitation, the upper layer of soap is called soap granules; The glycerol water with salt in the lower layer is discharged from the bottom of the soap pot to recover glycerol.
wash
After separating the waste liquid, add water and steam to boil the soap particles, causing them to transform from a separated state into a uniform soap gel, washing out residual glycerol, pigments, and impurities.
Alkaline precipitation
In order to completely saponifie the residual oil in the soap particles, glycerol, salt, pigments, and impurities inside the soap particles are further washed out by alkaline precipitation. The lowest concentration of alkali that completely precipitates from alkaline precipitation water is called the limit concentration of alkaline precipitation water.
Organize and adjust the electrolyte and fatty acid content in the soap particles after alkaline precipitation, reduce impurities, improve color, and obtain the maximum soap yield and qualified soap base. When organizing, an appropriate amount of electrolyte (such as caustic soda, salt) should be added, adjusted enough to cause the soap material to separate into two soap phases. The upper layer is pure soap base, and the lower layer is soap feet. The soap feet have a deep color and many impurities, and are usually reused during the next pot of alkaline precipitation.
forming
Soap base is condensed into large soap plates, then cut into soap blanks, printed and dried into laundry soap, soap and other products.
review
Soap is likely to have been first invented by the Egyptian people in the Nile Valley. Phoenician sailors brought the technology of making soap to the Mediterranean coast around 600 BC. In the 1st century AD, the highest quality soap was made by mixing goat fat with ash obtained from burning beech wood.
Before the end of the 18th century, soap was made from animal fat and wood ash. At the end of the 18th century, someone discovered that an alkali made from salt could replace wood ash. This type of alkali is called caustic soda. At that time, vegetable oils such as olive oil, palm oil, sesame oil, and soybean oil also began to replace animal fats.
Soap has a wide range of uses, in addition to the familiar use for washing clothes, it is also widely used in the textile industry. The sodium salt of higher fatty acids is usually used the most, commonly called hard soap; Its potassium salt is called soft soap and is commonly used for washing hair and shaving. Its ammonium salt is often used to make snow cream. Based on the composition of soap and considering the fatty acid content, soap made from saturated fatty acids is relatively hard; On the contrary, soap made from fatty acids with high unsaturation is softer. The main raw material of soap is oil with a high melting point. From the perspective of carbon chain length, generally speaking, the carbon chain of fatty acids is too short, resulting in soap with high solubility in water; If the carbon chain is too long, the solubility will be too low. Therefore, only potassium or sodium salts of C10-C20 fatty acids are suitable for making soap. In fact, soap contains the most sodium salts of C16-C18 fatty acids.
Soap usually contains a large amount of water. After adding spices, dyes, and other fillers to the finished product, various soaps are obtained.
The commonly used yellow laundry soap is generally mixed with rosin, which is added in the form of sodium salt to increase the solubility of soap and foam, and it is cheaper as a filler.
White laundry soap is made by adding sodium carbonate and water glass (with a content of up to 12%). Generally, laundry soap contains about 30% moisture. If the white laundry soap is dried and cut into thin slices, you will get soap slices, which can be used to wash high-end fabrics.
Adding an appropriate amount of a mixture of phenol and cresol (preservative, antibacterial) or boric acid to soap yields medicinal soap. Soap requires relatively advanced ingredients, such as mixing butter or palm oil with coconut oil to make soap. The soap is crushed, dried to a moisture content of about 10% to 15%, and then added with spices and dyes before being pressed into shape.
Liquid potassium soap is commonly used as shampoo and is usually made from coconut oil.
Soap is usually divided into three types: hard soap, soft soap, and fatty soap. If certain drugs are added to soap, it becomes medicated soap, such as sulfur soap, sandalwood soap, etc.
Hard soap, also known as "stinky soap", has a high alkaline content and strong ability to remove oil and dirt. However, it also has a significant irritant effect on the skin, and repeated use can quickly cause dryness, roughness, and peeling of the skin. Therefore, hard soap is generally only used for laundry and not for bathing.
Soft soap is the "soap" we usually use. It has a low alkaline content and minimal irritation to the skin, so it can be used by both normal individuals and psoriasis patients. It can have a good anti dandruff effect on skin lesions.
Fat soap, also known as high-fat soap, does not contain alkali. Children's soap mostly belongs to this category. Suitable for female patients.
Stone carbonate soap, sulfur soap, coal tar soap, boric acid soap, lisu soap, sandalwood soap and other medicinal soaps can also be used by psoriasis patients. But if patients are allergic to a certain type of medicated soap, they should avoid using it.
In China, there is still a certain market demand for fragrant soap in washing products, especially in rural and remote areas where people still use soap for washing their faces and bathing. In populous China, considering various factors, soap and soap are not instant products and should still be developed and improved accordingly. In the past decade, synthetic detergents in China have continued to increase at an annual rate of 8%. So Chinese washing products, especially various synthetic detergent products, are still promising in the foreseeable future.
wash hands
The significance of washing hands with soap
Pneumonia and diarrhea are the leading causes of death in children under the age of five. Every year, over 3.5 million children worldwide are unable to celebrate their 5th birthday due to diarrhea and pneumonia. Washing hands with soap can save the lives of millions of children. Hand washing can also prevent skin infections, eye infections, intestinal parasitic diseases, SARS and avian influenza, which is beneficial to the health of cancer patients and HIV carriers.
Washing hands with soap is a life-saving intervention that all countries and communities are technically and economically capable of. Advancing this measure is not only beneficial to health, but also because washing hands with soap makes people feel comfortable, reflects a person's social status and upbringing, and can bring people closer together.
After urinating, scrubbing the child's buttocks, and before touching food with hands, it is necessary to wash hands with soap or hand sanitizer in these three situations.
The benefits of washing hands with soap
Handwashing is the cornerstone of public health, and new hygiene practices and public health services were the main factors contributing to the rapid decline in infectious disease mortality rates in wealthy countries at the end of the 19th century. Like fecal isolation and safe handling, as well as providing sufficient purified water, washing hands with soap or hand sanitizer is one of the most effective ways to prevent diarrhea (reducing infection rates by up to half), and it is also the cheapest method. In addition, washing hands with soap can limit the spread of respiratory diseases (reducing infection rates by up to a quarter). Moreover, washing hands with soap or hand sanitizer is also a powerful barrier against other diseases such as worms, eye infections like sand eyes, and skin infections like pyoderma.
Soap hand washing cost
Washing hands with soap is the cheapest health intervention. Disability Adjusted Life Years (DALYs) are measures of disease burden and health intervention effectiveness by combining years of life lost and years of living with disability. Obviously, washing hands with soap is the most effective way to return DALYs associated with diarrhea. The cost of hand washing is significantly lower than that of immunization, for example, the cost of measles immunization for one DALY is between $250 and $4500. This is not to say that vaccination is unnecessary, but simply to point out that due to insufficient investment in promoting hand washing, we have missed an astonishing number of opportunities to save lives using the cheapest methods. Most families in the world can already afford soap, so cost is not a reason for people to wash their hands with soap.
