Soap has a wide range of uses. It is widely used in textile industry besides familiar washing clothes. Usually, the most advanced fatty acids are sodium salts, commonly called hard soap, which are called soft soap and are used for shampoo and shaving. Its ammonium salt is often used as a cream. According to the composition of the soap, the soap made by the saturated fatty acid is hard to make from the fatty acid part, and on the contrary, the soap made by the unsaturation fatty acid is softer. The main ingredient of the soap is the high melting point of the oil. Considering the length of carbon chain, in general, the carbon chain of fatty acids is too short, the soap made in the water is too soluble in the water, and the carbon chain is too long, so the solubility is too small. Therefore, only C10 ~ C20 fatty acids potassium salt or sodium salt are suitable for making soap. In fact, soap contains C16 ~ C18 fatty acids.
Soap usually contains a lot of water. After adding spices, dyes and other fillers to the finished products, all kinds of soap will be obtained.
Commonly used yellow laundry soap, usually mixed with rosin, is added in the form of sodium salt. The purpose is to increase the solubility and foam of the soap, and it is also cheaper as a filler.
White laundry soap is added with sodium carbonate and sodium silicate (with a content of 12%), which contains about 30% of the moisture in the laundry soap. If the white laundry soap is dried and cut into thin slices, the soap can be used to wash the high grade fabric.
Soap is added to the soap by adding proper amount of phenol and cresol mixture (antisepsis, sterilization) or boric acid. Soap needs to be more advanced materials, for example, using butter or palm oil and coconut oil mixed with coconut oil, made of soap, broken, dry to water content of about 10 to 15%, and then add spices, dyes, pressed molding is obtained.
Liquid potassium soap is commonly used as shampoo and so on, usually with coconut oil as raw material.
Soap, usually divided into hard soap, soft soap and soap three kinds. If you add some medicine into the soap, it will become a soap, such as sulfur soap, sandalwood soap and so on.
Hard soap is often said "smelly soap", it contains high alkalinity, the deoiling and decontamination ability is strong, but also has greater irritation to the skin, repeated use can make skin quickly dry, rough, desquamation and other phenomena. Therefore, hard soap is usually used for laundry but not for bathing.
Soft soap is the "soap" we usually use. It has lower alkalinity and less irritation to the skin, so it can be used in both normal and psoriatic patients. There is a good dandruff effect on the skin.
Fatty soap is also called multi - fat soap, not containing alkali. Children's soap belongs to this class. It is suitable for the use of female patients.
Carbolic soap, sulfur soap, coal tar soap, boric acid soap, Lai Su soap and sandalwood soap can also be used for psoriasis patients. But if the patient is allergic to some soap, it should be avoided.