Sodium Hydroxide
Title: Sodium Hydroxide
CAS Registry Number: 1310-73-2
Additional Names: Caustic soda; soda lye; sodium hydrate
Molecular Formula: HNaO
Molecular Weight: 40.00
Percent Composition: H 2.52%, Na 57.47%, O 40.00%
Line Formula: NaOH
Literature References: By reacting calcium hydroxide with sodium carbonate; from sodium chloride by electrolysis; from sodium metal and water vapor at low temp. Description of industrial processes: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 737-745. Toxicity: Fazekas, Arch. Exp. Pathol. Pharmakol. 184, 587 (1937).
Properties: Fused solid with crystalline fracture. Rapidly absorbs carbon dioxide and water from the air. Very corrosive (caustic) to animal and vegetable tissue and to aluminum metal in the presence of moisture. Sold as lumps, sticks, pellets, chips, etc. When kept in tight containers, the usual grades contain 97-98% NaOH. mp 318°. d25 2.13. One gram dissolves in 0.9 ml water, 0.3 ml boiling water, 7.2 ml abs alcohol, 4.2 ml methanol, also sol in glycerol. Generates considerable heat while dissolving, or when the soln is mixed with an acid. Volumetric NaOH solns used in the laboratory must be protected from air to avoid formation of carbonate. Concentrated NaOH solns dissolve practically no sodium carbonate. The pH of a 0.05% w/w soln ~12, of a 0.5% soln ~13, of a 5% soln ~14. Density, boiling and freezing pt data for (w/w) water solns. d415: 5% 1.056, 10% 1.111, 20% 1.222, 30% 1.333, 40% 1.434, 50% 1.530. bp: 5% 102°, 10% 105°, 20% 110°, 30% 115°, 40% 125°, 50% 140°. fp: 5% -4°, 10% -10°, 20% -26°, 30% 1°, 40% 15°, 50% 12°. LD orally in rabbits: 500 mg/kg (10% soln) (Fazekas).
Melting point: mp 318°
Boiling point: bp: 5% 102°, 10% 105°, 20% 110°, 30% 115°, 40% 125°, 50% 140°
Density: d25 2.13; d415: 5% 1.056, 10% 1.111, 20% 1.222, 30% 1.333, 40% 1.434, 50% 1.530
Toxicity data: LD orally in rabbits: 500 mg/kg (10% soln) (Fazekas)
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin and mucous membranes; pneumonitis; eye and skin burns; temporary loss of hair. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-1140, 1997) p 284.
Use: NaOH solutions are used to neutralize acids and make sodium salts, e.g., in petroleum refining to remove sulfuric and organic acids; to treat cellulose in making viscose rayon and cellophane; in reclaiming rubber to dissolve out the fabric; in making plastics to dissolve casein. NaOH solns hydrolyze fats and form soaps; they precipitate alkaloids (bases) and most metals (as hydroxides) from water solns of their salts. Pharmaceutic aid (alkalizer).
Therap-Cat-Vet: Caustic; dehorning of calves.

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