Sodium hydroxide, chemical formula NaOH, commonly known as caustic soda, caustic soda, caustic soda, a strong corrosive alkali, usually flake or block form, easily soluble in water (dissolved in water and heat) form an alkaline solution, otherwise deliquescence, easy to absorb the water vapor in the air (deliquescence) and carbon dioxide (), adding hydrochloric acid modification to test whether the metamorphism.
NaOH is one of the essential chemicals in the chemical laboratory and one of the common chemicals. The pure products are colorless and transparent crystals. The density is 2.130g/cm3. The melting point is 318.4 degrees centigrade. The boiling point is 1390 degrees centigrade. Industrial products contain a small amount of sodium chloride and sodium carbonate, which are white opaque crystals. It has lumpy, flaky, grainy, and rod like. The amount is 39.997.
Sodium hydroxide can be used as an alkaline detergent in water treatment, soluble in ethanol and glycerol, and insoluble in propanol and ether. Disproportionation reaction with halogens such as chlorine, bromine and iodine. Neutralize the acid with the acid and produce salt and water.
Sodium hydroxide (NaOH) is widely used. It is used for the production of paper, soap, dyestuff, rayon, smelting metal, petroleum refining, cotton fabric finishing, purification of coal tar products, and food processing, wood processing and machinery industry.
It can be used as a chemical experiment. Except for reagents, because it has strong water absorption and deliquescence, also can be used as the basic desiccant.  can also absorb acid gas (as in the experiment that sulfur is burned in oxygen, sodium hydroxide solution can be loaded into a bottle to absorb toxic sulfur dioxide).
Neutral, alkaline gas mixed with CO?, the use of NaOH removal of miscellaneous, generating Na? CO? (sodium carbonate) and H? O (generated Na? CO? In H? O):
CO? +2NaOH = Na? CO? +H? O; H2O+CO2+Na2CO3=2NaHCO3
Sodium hydroxide is widely used in the national economy, and sodium hydroxide is needed in many industrial sectors. The Department that uses the most sodium hydroxide is the manufacture of chemical drugs, followed by paper making, aluminum smelting, tungsten smelting, rayon, artificial cotton and soap manufacturing. In addition, in the production of dyes, plastics, pharmaceutical and organic intermediates, old rubber regeneration, metal sodium, the electrolysis of water and inorganic salt production, preparation of borax, chromium salt, manganese salt, phosphate, also want to use a lot of caustic soda. At the same time, sodium hydroxide is one of the most important raw materials for producing polycarbonate, super absorbent polymer, zeolite, epoxy resin, sodium phosphate, sodium sulfite and a large amount of sodium salt.
Soap: making soap is the oldest and most widely used use of caustic soda.
Sodium hydroxide has been used in the traditional use of life. Until today, the demand for soap, soap and other kinds of washing products still accounts for about 15% of caustic soda.
The main ingredient of fat and vegetable oil is triglyceride (three acyl glycerol), and its alkaline hydrolysis equation is as follows:
(RCOO) 3C3H5 (fat) +3NaOH=3 (RCOONa) (advanced fatty acid) +C3H8O3 (glycerol)
This reaction is the principle of the production of soap, so it is named saponification reaction.
The R base may be different, but the generated R-COONa can make soap. The common R- has:
C17H33-:8- seventeen carbenyl group. R-COOH is oleic acid.
C15H31-: positive fifteen alkyl. R-COOH palmitate.
C17H35-: positive seventeen alkyl. R-COOH is stearic acid.
Detergent: sodium hydroxide is used to produce various detergents, and even today's washing powder (twelve alkylbenzene sulfonate and other ingredients) is also made by a large number of caustic soda. Caustic soda is neutralized after the sulfonation reaction.
Sodium hydroxide plays an important role in the paper industry. Because of its basic characteristics, it is used to cook and bleach the pages of paper.
The raw materials for paper making are wood or grass plants. In addition to cellulose, these plants contain quite a lot of non cellulose (lignin, gum and so on). The dilute sodium hydroxide solution can dissolve the non cellulose components and separate the pulp, thus making the pulp of cellulose as the main component. 
Artificial fiber and textile
Rayon fibers, such as synthetic cotton, artificial wool and rayon, are mostly viscose fibers. They are made of viscose liquid from cellulose, sodium hydroxide and carbon disulfide (CS2). They are made by spinning and condensation.
In the textile industry, sodium hydroxide is used for the treatment and dyeing of fiber, and is used for mercerizing treatment of cotton fibers. Cotton fabric is treated with caustic soda solution, which can remove waxes, Oils and starches and other substances covered on cotton fabric. Meanwhile, it can increase the mercerizing and color of fabrics and make dyeing more uniform. 
After washing the oil products, they also contain some acidic substances, which must be washed with sodium hydroxide solution and then washed by water to get the refined product. 
The hygienic standard for the use of food additives in China (GB 2920-1996) stipulates that it can be used as a processing aid and is used in proper amount according to the needs of production.
Sodium hydroxide can be widely used in the production process: the cleaning process of the container; the processing process of starch; preparation of carboxymethyl cellulose; monosodium glutamate manufacturing process. 
Sodium hydroxide is widely used in water treatment. In a sewage treatment plant, sodium hydroxide can reduce the hardness of water by neutralizing reaction. In the field of industry, it is a regenerative agent for the regeneration of ion exchange resin. Sodium hydroxide has strong alkalinity and has relatively high solubility in water. As sodium hydroxide has relatively high solubility in water, it is easy to measure the amount of sodium, which can be easily made in various fields of water treatment.
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