Caustic soda is also known as sodium hydroxide, the chemical formula is NaOH, generally in the form of flakes or particles, easily soluble in water (dissolving in water, exothermic) and forming an alkaline solution, and deliquescence, easy to absorb water vapor in the air . NaOH is one of the necessary chemicals in chemical laboratories, and it is also one of the common chemicals. Pure products are colorless and transparent crystals. Density 2.130g/cm³. Melting point 318.4 ℃. Boiling point 1390 ℃. Industrial products contain a small amount of sodium chloride and sodium carbonate, which are white opaque crystals. There are blocks, flakes, granules and rods, etc. Formula 40.01.
Sodium hydroxide can be used as an alkaline cleaning agent in water treatment, soluble in ethanol and glycerol; insoluble in propanol and ether. It also has a corrosive effect on carbon and sodium at high temperatures. It disproportionates with halogens such as chlorine, bromine and iodine. Neutralizes with acids to generate salt and water.
The main purpose:
Caustic soda has a wide range of uses. It is used in papermaking, soap, dyes, rayon, aluminum, petroleum refining, cotton fabric finishing, purification of coal tar products, as well as food processing, wood processing and machinery industry.
Chemistry experiment
In addition to being used as a reagent, it can also be used as an alkaline desiccant due to its strong water absorption and deliquescence. It can also absorb acid gases (such as in the experiment of burning sulfur in oxygen, sodium hydroxide solution can be bottled to absorb toxic sulfur dioxide.)
Industrial
Sodium hydroxide is widely used in the national economy, and many industrial sectors require sodium hydroxide. The sector that uses the most sodium hydroxide is the manufacture of chemicals, followed by the manufacture of paper, aluminum, tungsten, rayon, rayon and soap. In addition, in the production of dyes, plastics, pharmaceuticals and organic intermediates, the regeneration of old rubber, the production of sodium metal, the electrolysis of water and the production of inorganic salts, the production of borax, chromium salts, manganates, phosphates, etc., should also be used. Lots of caustic soda.
Chemical industry
The characteristics of sodium hydroxide determine that this product is an indispensable and important substance in a large number of chemical reactions. Sodium hydroxide is one of the important raw materials for the production of polycarbonate, superabsorbent polymers, zeolites, epoxy resins, sodium phosphate, sodium sulfite and a large number of sodium salts.
Oleic acid is a monounsaturated fatty acid, which is obtained by hydrolysis of oil; soft and stearic acid are saturated fatty acids, which are obtained by hydrolysis of fat.
If potassium hydroxide is used for hydrolysis, the resulting soap is soft.
Adding sodium chloride to the solution can reduce the solubility of the fatty acid salt and separate the fatty acid salt, a process called salting out. Higher fatty acid salts are the main components of soap, which can be treated with fillers to obtain bar soap.
Saponification reaction
The main component of fat and vegetable oil is triglyceride, and its alkaline hydrolysis equation is:
The R groups may be different, but the resulting R-COONa can be used as soap. Common R- are:
C17H33-: 8-heptadecenyl. R-COOH is oleic acid.
C15H31-: n-pentadecyl. R-COOH is palmitic acid.
C17H35-: n-heptadecyl. R-COOH is stearic acid.
Absorb carbon dioxide gas
Neutral and alkaline gases are mixed with CO₂, the following reaction can be used to remove impurities:
CO₂+2NaOH = Na₂CO₃+H₂O
Papermaking
Sodium hydroxide plays an important role in the paper industry. Due to its alkaline properties, it is used in the process of boiling and bleaching paper sheets.
Food industry
Sodium hydroxide can be widely used in the following production processes: the cleaning process of containers; the processing process of starch; the preparation process of carboxymethyl cellulose; the manufacturing process of sodium glutamate.
Water treatment
Sodium hydroxide is widely used in water treatment. In sewage treatment plants, sodium hydroxide can reduce the hardness of water through a neutralization reaction. In the industrial field, it is a regenerant for ion exchange resin regeneration. Sodium hydroxide is strongly alkaline and relatively soluble in water. Because caustic soda is in liquid state, it is easy to measure the dosage and it is conveniently used in various fields of water treatment.
Sodium hydroxide is used in the following subjects in water treatment: elimination of water hardness; adjustment of pH value of water; neutralization of wastewater; regeneration of ion exchange resin; elimination of heavy metal ions in water by precipitation.
Man-made fibers and textiles
In the textile industry, sodium hydroxide is used for final treatment and dyeing of fibers. Main application: mercerized man-made fibers.
Mmetallurgy
Sodium hydroxide is used to treat bauxite, which contains alumina, in which aluminum metal is present. Aluminum (the second most used metal in the world. Sodium hydroxide is also used to produce zinc alloys and zinc ingots.
Cleaning Products
Sodium hydroxide has been used for traditional daily purposes, and until today, the demand for caustic soda in soaps, soaps and other types of washing products still accounts for about 15% of caustic soda.
Soap: The oldest and most widespread use of caustic soda is the manufacture of soap, in which it is used to neutralize fatty acids.
Detergents: Sodium hydroxide is used in the production of various detergents, and even today's laundry detergents are made from large amounts of caustic soda, which is used to neutralize excess oleum after the vulcanization reaction.
