Selenious acid Chemical Properties

Melting point:

70 °C (dec.) (lit.)

Boiling point:

684.9 °C(lit.)

Density 

3.004 g/mL at 25 °C (lit.)

vapor pressure 

2.7hPa at 15℃

Flash point:

690°C

storage temp. 

Store at RT.

solubility 

H₂O: soluble

form 

powder

pka

2.46(at 25℃)

color 

White to almost white or light pink

Specific Gravity

3.004

PH

3.15(1 mM solution);2.47(10 mM solution);1.9(100 mM solution)

Water Solubility 

167 g/100 mL (20 ºC)

Sensitive 

Hygroscopic

Merck 

14,8430

Exposure limits

ACGIH: TWA 0.2 mg/m3
NIOSH: IDLH 1 mg/m3; TWA 0.2 mg/m3

Stability:

Stable.

CAS DataBase Reference

7783-00-8(CAS DataBase Reference)

EPA Substance Registry System

Selenious acid (H2SeO3) (7783-00-8)

Safety Information

Hazard Codes 

T,N,Xi

Risk Statements 

36/38-50/53-33-23/25-52/53

Safety Statements 

61-60-45-28A-20/21-26-28

RIDADR 

UN 3440 6.1/PG 3

WGK Germany 

3

RTECS 

VS7700000

F 

3

TSCA 

Yes

HazardClass 

8

PackingGroup 

III

HS Code 

28111980

Hazardous Substances Data

7783-00-8(Hazardous Substances Data)

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ACROS
• Language:English Provider:ALFA

Selenious acid Usage And Synthesis

Description

Selenious acid is a colourless, deliquescent crystal in appearance. It decomposes on heating, producing water and toxic fumes of selenium oxides.
It is incompatible with strong reducing agents, organic materials, and finely powdered metals and reacts on contact with acids producing toxic gaseous hydrogen selenide. Selenious acid is a non-combustible chemical. On fire/burning, it emits irritating or toxic fumes (or gases).
The major use of selenious acid is in changing the colour of steel, especially the steel in guns from silver grey to blue grey. It is also used for the chemical darkening and patination of copper brass and bronze, producing a rich dark-brown colour that can be further enhanced with mechanical abrasion.

Chemical Properties

Selenious acid is a colorless, crystalline solid.

Chemical Properties

White solid

Uses

As an oxidizing agent, as a reagent for alkaloidsSelenous acid is used in steel guns, wherein it changes the color of the steel from silver-grey to blue-grey. It serves as an important component of the Mecke reagent, which is utilized for drug testing. It acts as a source of selenium. It acts as a reagent for alkaloids and an oxidizing agent. Further, it is used in labeling radiopharmaceuticals. It is involved in the organic synthesis for the preparation of glyoxal.

Uses

As a reagent for alkaloids; as oxidizing agent.

Definition

ChEBI: Selenous acid is a selenium oxoacid. It is a conjugate acid of a hydrogenselenite.

General Description

Colorless solid, transparent, colorless crystals. Used as a reagent for alkaloids and as an oxidizing agent. Isotope is used in labeling radiopharmaceuticals.

Reactivity Profile

Selenious acid decomposes when heated to toxic and volatile selenium dioxide. Serves as an oxidizing agent. Reacts exothermically with many reducing agents including hydroiodic acid, sulfurous acid, sodium hyposulfite, hydroxylamine salts, hydrazine salts, hypophosphorous acid, phosphorous acid [Merck]. Oxidizes many organic substances. Is oxidized to selenic acid by strong oxidizing agents.

Hazard

Toxic by inhalation, ingestion, and skin absorption.

Health Hazard

Selenious acid and its salts are capable of penetrating the skin and can produce acute poisonings. Causes irritations and burns of the skin. It is highly toxic orally. Inorganic selenium compounds may cause dermatitis.

Fire Hazard

When heated to decomposition Selenious acid emits toxic fumes of selenium. Avoid heating.

Safety Profile

Poison by ingestion, intraperitoneal, and intravenous routes. Human mutation data reported. Used as an oxidizing agent. When heated to decomposition it emits toxic fumes of Se. See also SELENIUM COMPOUNDS

Potential Exposure

Selenious acid is used as a reagent for alkaloids and as an oxidizing agent. Isotope is used in labeling radiopharmaceuticals.

Shipping

UN3283Selenium compound, solid, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous material, Technical Name Required. UN3440 Selenium compound, liquid, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous material, Technical Name Required.

Purification Methods

Recrystallise the acid from water. On heating it loses water and SeO2 sublimes. [Waitkins & Clark Chem Rev 36 235 1945.]

Incompatibilities

A strong oxidizer. Reacts exothermically with many reducing agents including hydroiodic acid, sulfurous acid, sodium hyposulfite, hydroxylamine salts, hydrazine salts, hypophosphorous acid, phosphorous acid. Incompatible combustibles, organic material, oxidizable materials, strong acids, strong bases. Contact with acids produce toxic and gaseous hydrogen selenide. Attacks metals.

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal.

Selenious acid(7783-00-8)Related Product Information

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• Sodium selenate
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• Selenious acid anhydride
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• COPPER(II) SELENATE
• Selenious acid calcium salt