Sodium hydroxide (NaOH), also known as lye and caustic soda, is an inorganic compound. It is a white solid and highly caustic metallic base and alkali salt of sodium which is available in pellets, flakes, granules, and as prepared solutions at a number of different concentrations. Sodium hydroxide forms an approximately 50% (by weight) saturated solution with water.; Sodium hydroxide is soluble in water, ethanol, and methanol. This alkali is deliquescent and readily absorbs moisture and carbon dioxide in air.
Sodium hydroxide is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner. Worldwide production in 2004 was approximately 60million tonnes, while demand was 51million tonnes.

Chemical Name	sodium hydroxide
Synonyms	NaOH;caustic soda;Sodium hydroxide;
CAS No.	1310-73-2
Molecular Formula	HNaO
Molecular Weight	39.99710
PSA	23.06000
LogP	-0.17680

RTECS number	WB4900000
PubChem number	24857963
EINECS number	215-185-5
MDL number	MFCD00003548

Appearance & Physical State	odourless white waxy, opaque crystals (often sold as pellets)
Density	2.13 g/cm3
Boiling Point	1388ºC
Melting Point	318ºC
Flash Point	N/A
Refractive Index	1.473-1.475
Water Solubility	418 g/L (0 °C), 1110 g/L (20 °C), 3370 g/L (100 °C)
Soluble	soluble in methanol and glycerol, negligible in ammonia, insoluble in ether
Storage Condition	2-8ºC
Vapor Density	<1 (vs air)
Vapor Pressure	1 mm Hg ( 745 °C)

RTECS	TT2975000
Hazard Class	8
Safety Statements	S24/25-S37/39-S45
HS Code	2815110000
WGK Germany	1
Packing Group	II
RIDADR	UN 1823
Risk Statements	R35
Hazard Codes	C
Symbol	GHS05
Signal Word	Danger
Caution Statement	P260; P280; P303 + P361 + P353; P304 + P340 + P310; P305 + P351 + P338 + P310
Hazard Declaration	H290; H314