Phosphorus trioxide Chemical Properties

Melting point:

23.8°

Boiling point:

bp 173.1° in nitrogen atm

Density 

d421 2.135

solubility 

reacts with H2O

form 

colorless monoclinic crystals or liquid

color 

colorless monoclinic crystals, crystalline or liquid

Water Solubility 

slowly forms H3PO3 in cold H2O; reacts violently in hot H2O forming red P, PH3, and H3PO4 [MER06]

crystal system

Monoclinic

Space group

P21/m

Lattice constant

a/nm	b/nm	c/nm	α/o	β/o	γ/o	V/nm3
0.643	0.7887	0.6812	90	106.01	90	0.3321

EPA Substance Registry System

Phosphorus trioxide (1314-24-5)

Safety Information

RIDADR 

2578

HazardClass 

8

PackingGroup 

III

Phosphorus trioxide Usage And Synthesis

Chemical Properties

transparent crystal(s); monoclinic or colorless liquid; disproportionates to red P and P2O4if heated above 210°C [MER06]

General Description

White crystalline solid or a liquid (melting point 24°C). Density 2.14 g / cm3. Toxic and corrosive. May severely irritate skin and eyes. Used to make other chemicals.

Air & Water Reactions

Fumes in air. Reacts slowly with cold water to give phosphorous acid. Reacts vigorously with hot water to generate red phosphorus, phosphine (highly toxic and flammable) and phosphoric acid [Merck 11th ed. 1989].

Reactivity Profile

Phosphorus trioxide reacts exothermically with bases. Melted Phosphorus trioxide readily ignites in air. Instantly ignites with a flame of almost blinding brilliance when thrown into oxygen at 50-60°C [J. Am. Chem. Soc. 125:347. 1924]. Incompatible with ammonia, disulfur dichloride, halogens, oxygen, phosphorus pentachloride, sulfur, sulfuric acid, water [Bretherick, 5th ed., 1995, p. 1778].

Health Hazard

TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. Reaction with water or moist air will release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars etc.). Substance will react with water (some violently), releasing corrosive and/or toxic gases and runoff. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.

Phosphorus trioxide(1314-24-5)Related Product Information

• Boron oxide
• Iodine pentafluoride
• Nitrogen trifluoride
• Carbon tetrafluoride
• Oxygen difluoride
• IODINE HEPTAFLUORIDE
• Trichlorine nitride
• COBALT(III) OXIDE BLACK