Sodium hydroxide
Synonyms: Aetznatron;Augus hot rod;causticflake;causticsoda,bead;causticsoda,bead(dot);causticsoda,dry(dot);causticsoda,flake(dot);causticsoda,granular(dot)
CAS: 1310-73-2
MF: HNaO
MW: 40
EINECS: 231-659-4
Melting point 681 °C(lit.)
Boiling point 145 °C
density 1.515 g/mL at 20 °C
vapor density <1 (vs air)
vapor pressure 1 mm Hg ( 745 °C)
refractive index 1,473-1,475
storage temp. 2-8°C
solubility H2O: 1 M at 20 °C, clear, colorless
form beads
Water Solubility SOLUBLE
Sensitive Air Sensitive & Hygroscopic
Merck 14,8627
Characteristic Pure anhydrous sodium hydroxide is white translucent, crystalline solid with strong corrosive property. It is hydroscopic and can be used as a kind of desiccant but can’t be used for dry sulfur dioxide, carbon dioxide and hydrogen chloride gas. It is also easy to subject to deliquescence in the air. Sodium hydroxide is very easily soluble in water with solubility increasing with the increasing temperature and dissolving being able to release a lot of heat. Upon 288K, its saturated solution concentration can reach 16.4mol/L (1:1). Its solution exhibits astringency and creamy feeling and is strongly alkaline with all the property of alkali. Commercially available caustic soda includes both solid type and liquid type: pure solid caustic soda is white, bulk, flake, rod, granular, and crisp; pure liquid caustic soda is colorless and transparent liquid. Sodium hydroxide is also easily soluble in ethanol and glycerol but insoluble in ether, acetone, and liquid ammonia. It has corrosive effect on fiber, skin, glass, and ceramics with dissolving or dilution of concentrated solution being able to release heat; its neutralization reaction of inorganic acid can produce a lot of heat to form the corresponding salts; it can react with metal aluminum and zinc metal, non-metallic boron and silicon to release hydrogen; it can also have disproportionation reaction with chlorine, bromine, iodine and the other halogen. It can precipitate the metal ions from the aqueous solution to generate hydroxides; it can have saponification reaction with oil to generate corresponding organic acid salt and ethanol which is the basic principle for removing the oil on the fabric.
Uses Industrial-purpose sodium hydroxide should meet the national standard GB 209-2006; the caustic soda produced from industrial-used ion-exchange membrane method should meet the national standard GB/T11199-89; fiber used sodium hydroxide should meet the national standard 11212-89; edible sodium hydroxide should meet the national standard GB 5175-85.
In industry, sodium hydroxide is commonly referred to as caustic soda. This is because when concentrated sodium hydroxide solution is spilled to the skin, it will corrode the skin surface and cause burn wound. It has dissolving ability on protein. It is strongly irritant and corrosive (because of its proteins dissolution, compared with the acid burn wound, alkali burn wound is more difficult for healing). When 0.02% solution gets into the rabbit eyes, it can cause corneal epithelial damage. Intraperitoneal-mice LD50: 40 mg/kg, rabbit-oral LDLo: 500 mg/kg. Its dust can stimulate eye and respiratory tract and cause nasal septum corrosion; when spilled on the skin, especially spilled to the mucous membranes, it can result in soft crust and can penetrate deep tissue which leaving scars after burns; when being splashed into eyes, it can not only damage the cornea, but also destroy the deep tissue of eyes with causing blindness in severe cases; Misuse can cause gastrointestinal burns, colic, mucosal erosion, vomiting of hemorrhagic stomach content, bloody diarrhea, and sometimes hoarse occur, difficulty swallowing, shock, gastrointestinal perforation, as well as intestinal stenosis in late period. Owing to the strong alkaline, it can result in water pollution. Plants and aquatic organisms should be pay special attention.