Nomenclature
CAS number: 1310-73-2
Sodium hydroxide (Na(OH)); Caustic soda; soda lye; sodium hydrate.
HNaO; mol wt 40.00.
H 2.52%, Na 57.47%, O 40.00%.
NaOH.
Description and 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).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).
Analytical uses as alkalimetric titrant, buffer, and pH modifier.
Therapeutic Category (Veterinary)
Caustic; dehorning of calves.