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Sulfates and sulfur salts

Selenium dioxide

Also known as Selenious anhydride, Selenium oxide (SeO2), Selenium dioxide dimer

CAS 7446-08-4Formula O2SeMolar mass 110.96 g/molEC 231-194-7
GHS signal word: Danger. Pictograms: Corrosive, Acute toxicity (severe), Serious health hazard, Hazardous to the environment 47 suppliers listed
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Selenium dioxide chemical structure, O2Se, CAS 7446-08-4
2D chemical structure

Key facts

What buyers check first

All properties
Appearance
Lustrous tetragonal needles, yellowish green vapor
Melting point
340 ยฐC
Boiling point
315 ยฐC
Density
Density (at 15 ยฐC): 3.95 g/cmยณ
Solubility
In water, 400 g/L at 20 ยฐC
HS code
285390
Category
Sulfates and sulfur salts
UN number
UN 3283
Illustrative photo, green pigment powder in a glass jar on a laboratory bench
Typical packagingIllustrative packaging image, not the actual product

What is Selenium dioxide?

Plain description, key identifiers and synonyms

Selenium dioxide appears as a white or creamy-white volatile lustrous crystal or crystalline powder with a pungent sour smell. Melting point 340 deg C. Density 3.954 g / cm3. Toxic by ingestion and inhalation.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
selenium dioxide
CAS number
7446-08-4 CAS number cross-checkedOther or deprecated CAS: 12640-89-0
EC numbers
231-194-7, 235-738-4
Molecular formula
O2Se
UNII
9N3UK29E57
MDL number
MFCD00003562
InChIKey
JPJALAQPGMAKDF-UHFFFAOYSA-N
InChI
InChI=1S/O2Se/c1-3-2
SMILES (canonical and isomeric)
O=[Se]=O

Synonyms

  • Selenious anhydride
  • Selenium oxide (SeO2)
  • Selenium dioxide dimer
  • Selenous acid anhydride
  • Selenium oxide (Se2O4)
  • Selenium(IV) dioxide (1:2)
  • Selenium oxide (1:2)
  • Oxide, Selenium
  • (oxo-lambda4-selanylidene)oxidane
  • Dioxide, Selenium
  • Selenium(IV) oxide
  • Selenium oxide
  • Oxoselane oxide
  • Selenium(IV) dioxide
  • RCRA waste number U204
  • Selenium (IV) oxide
  • Seleniumdioxide
  • Selenonyl
  • seleninyl oxygen
  • dioxido de selenio
  • Oxoselane oxide #
  • biossido di selenio
  • dioxyde de selenium
  • O2Se
  • Selenium oxide, SeO2
Show all 32 synonyms
  • selenium (IV) dioxide
  • Selenium dioxide, puriss., 98%
  • Selenium(IV) oxide (99.999%-Se)
  • Selenium dioxide, reagent grade, powder, 98%
  • Selenium dioxide, >=99.9% trace metals basis
  • Selenium dioxide, 99.999% trace metals basis
  • Selenium dioxide, ReagentPlus(R), powder, 99.8% trace metals basis

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

Appearance
Lustrous tetragonal needles, yellowish green vaporexp.
Odour
Vapor has a pungent sour smellexp.
Taste
Acidic taste, leaves a burning sensation.exp.
Melting point
340 ยฐCexp.
Boiling point
315 ยฐCexp.
Density
Density (at 15 ยฐC): 3.95 g/cmยณexp.
Solubility
In water, 400 g/L at 20 ยฐCexp.
Vapour pressure
12.5 mm Hg at 70 ยฐC, 20.2 mm Hg at 94 ยฐC, 39.0 mm Hg at 181 ยฐC, 760 mm Hg at 315 ยฐC, 848 mm Hg at 320 ยฐCexp.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
110.96 g/molcalc.
Exact mass
111.9064 Dacalc.
LogP (octanol/water)
-0.62calc.
Topological polar surface area
34.14 ร…ยฒcalc.
Hydrogen bond donors
0calc.
Hydrogen bond acceptors
2calc.
Rotatable bonds
0calc.
Heavy atoms
3calc.
Rings
0calc.
Aromatic rings
0calc.
Fraction sp3 carbons
0calc.
Formal charge
0calc.
Stereocentres
0calc.

Calculated for screening. Confirm critical figures with the supplier.

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Danger
GHS05: Corrosive
Corrosive
GHS06: Acute toxicity (severe)
Acute toxicity (severe)
GHS08: Serious health hazard
Serious health hazard
GHS09: Hazardous to the environment
Hazardous to the environment

Hazard statements

  • H301Toxic if swallowed.
  • H314Causes severe skin burns and eye damage.
  • H318Causes serious eye damage.
  • H331Toxic if inhaled.
  • H373May cause damage to organs through prolonged or repeated exposure.
  • H400Very toxic to aquatic life.
  • H410Very toxic to aquatic life with long lasting effects.
Precautionary statements (23)
  • P260Do not breathe dust, fume, gas, mist, vapours or spray.
  • P261Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264Wash skin thoroughly after handling.
  • P264 + P265Wash skin thoroughly after handling. Do not touch eyes.
  • P270Do not eat, drink or smoke when using this product.
  • P271Use only outdoors or in a well-ventilated area.
  • P273Avoid release to the environment.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P301 + P316If swallowed: Get emergency medical help immediately.
  • P301 + P330 + P331If swallowed: Rinse mouth. Do not induce vomiting.
  • P302 + P361 + P354If on skin: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
  • P304 + P340If inhaled: Remove person to fresh air and keep comfortable for breathing.
  • P305 + P354 + P338If in eyes: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P316Get emergency medical help immediately.
  • P317Get medical help.
  • P319Get medical help if you feel unwell.
  • P321Specific treatment (see supplemental first aid instructions on the label).
  • P330Rinse mouth.
  • P363Wash contaminated clothing before reuse.
  • P391Collect spillage.
  • P403 + P233Store in a well-ventilated place. Keep container tightly closed.
  • P405Store locked up.
  • P501Dispose of contents and container in accordance with local regulations.
UN number
UN 3283
Transport hazard class
6.1
Packing group
II

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Selenium dioxide suppliers

Sponsored listings first, then the documented ranking: membership, verification, replies, completeness, freshness and ratings

All 47 suppliers
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Where suppliers are based

47 suppliers in 13 countries

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Selenium dioxide price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

In the manufacture of other selenium compounds.

Analysis (testing for alkaloids), oxidizing agent, antioxidant in lubricating oils, catalyst.

Added to baths used in etching, formation of decorative colors on galvanized iron and nonferrous metals and alloys, and corrosion-protective coatings in magnesium alloys, synthesis of drug products, used in the manufacture of cortisone and nicotinic acid (niacin).

How it is made

Selenium dioxide, SeO2, is prepared by burning selenium in a current of air or oxygen and, optionally, by passing it over a catalyst or by oxidation with nitric acid to selenous acid followed by evaporation to dryness by heating.

Prepared by burning selenium in oxygen, ... by burning selenium in oxygen and nitrogen dioxide.

Regulatory status

Inventories, regulations and trade controls that list this substance

United States

  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Selenium dioxide is traded under.

HS 2853.90Indicative HS code

Phosphides, whether or not chemically defined, excluding ferrophosphorus, other, other

World exports in 2024
$2.45B
โˆ’33.6% vs 2023, imports $816M
2019 to 2024
Top exporters
  1. China68.4%
  2. Israel8.1%
  3. United States4.9%
Top importers
  1. United States19.3%
  2. Japan17.9%
  3. China13.4%
Reported customs values in USD, not prices.Full trade data

The HS code shown for Selenium dioxide is indicative (it is known at chapter level only). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Selenium dioxide, based on the data on this page

What is Selenium dioxide?

Selenium dioxide appears as a white or creamy-white volatile lustrous crystal or crystalline powder with a pungent sour smell. Melting point 340 deg C. Density 3.954 g / cm3. Toxic by ingestion and inhalation.

What is the CAS number of Selenium dioxide?

The CAS registry number of Selenium dioxide is 7446-08-4. Other or deprecated CAS numbers: 12640-89-0.

What is the molecular formula and weight of Selenium dioxide?

The molecular formula of Selenium dioxide is O2Se and its molar mass is 110.96 g/mol.

What is Selenium dioxide used for?

In the manufacture of other selenium compounds. Analysis (testing for alkaloids), oxidizing agent, antioxidant in lubricating oils, catalyst.

Is Selenium dioxide hazardous?

Selenium dioxide carries the GHS signal word "Danger". Main hazards: toxic if swallowed, causes severe skin burns and eye damage, causes serious eye damage. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Selenium dioxide?

Selenium dioxide is usually classified under HS code 285390 (Phosphides, whether or not chemically defined, excluding ferrophosphorus, otherโ€ฆ). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Selenium dioxide?

CompoundList lists 47 suppliers of Selenium dioxide in India, China, United States, Germany and 9 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Selenium dioxide in India?

12 suppliers in India list Selenium dioxide on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Selenium dioxide?

Suppliers quote Selenium dioxide on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

Practical guides that help when you source, ship or handle Selenium dioxide

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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