Selenium trioxide Property

Melting point:

118°C

Boiling point:

decomposes at 180℃ [CRC10]

Density 

3.440

solubility 

soluble in H2O, organic solvents

form 

white tetragonal crystals

color 

white tetragonal crystals, crystalline; hygroscopic

Water Solubility 

dissolves in H2O forming selenic acid [KIR82]

crystal system

square

Space group

P421c

Lattice constant

a/nm	b/nm	c/nm	α/o	β/o	γ/o	V/nm3
0.9636	0.9636	0.528	90	90	90	0.4903

EPA Substance Registry System

Selenium oxide (SeO3) (13768-86-0)

Safety

RIDADR 

3283

HazardClass 

6.1

PackingGroup 

II

Hazard and Precautionary Statements (GHS)

Selenium trioxide Chemical Properties,Usage,Production

Chemical Properties

white crystal(s); hygroscopic; can be prepared by reacting SO3 with potassium selenate or phosphorus pentoxide with selenic acid; strong oxidizing agent; stable in dry air at room temperatures; decomposes, if heated, first to selenium pentoxide, then to the dioxide [KIR82]

General Description

White Solid.

Air & Water Reactions

Reacts vigorously with water to form selenic acid solution.

Reactivity Profile

Inorganic oxidizing agents, such as Selenium trioxide, can react with reducing agents to generate heat and products that may be gaseous (causing pressurization of closed containers). The products may themselves be capable of further reactions (such as combustion in the air). The chemical reduction of materials in this group can be rapid or even explosive, but often requires initiation (heat, spark, catalyst, addition of a solvent). Explosive mixtures of inorganic oxidizing agents with reducing agents often persist unchanged for long periods if initiation is prevented. Such systems are typically mixtures of solids, but may involve any combination of physical states. Some inorganic oxidizing agents are salts of metals that are soluble in water; dissolution dilutes but does not nullify the oxidizing power of such materials. Organic compounds in general have some reducing power and can in principle react with compounds in this class. Actual reactivity varies greatly with the identity of the organic compound. Inorganic oxidizing agents can react violently with active metals, cyanides, esters, and thiocyanates.

Health Hazard

Absorption of selenium may be demonstrated by presence of the element in the urine and by a garlic-like odor of breath. Inhalation can cause bronchial spasms, symptoms of asphyxiation, and pneumonitis. Acute symptoms of ingestion include sternal pain, cough, nausea, pallor, coated tongue, gastrointestinal disorders, nervousness and conjunctivitis. Contact with eyes or skin causes irritation.