World Library  
Flag as Inappropriate
Email this Article

Selenous acid

Article Id: WHEBN0002798935
Reproduction Date:

Title: Selenous acid  
Author: World Heritage Encyclopedia
Language: English
Subject: Selenium dioxide, Selenium, Selenites, Selenite, Selenite (ion)
Collection: Hydrogen Compounds, Oxidizing Acids, Oxidizing Agents, Selenites
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Selenous acid

Selenous acid[1]
Structural formula
Ball-and-stick model
Names
IUPAC name
Selenous acid
Identifiers
 Y
ChEBI  Y
ChemSpider  Y
Jmol-3D images Image
KEGG  Y
PubChem
UNII  Y
Properties
H2SeO3
Molar mass 128.97 g/mol
Appearance white hygroscopic crystals
Density 3.0 g/cm3
Melting point decomposes at 70°C
very soluble
Solubility soluble in ethanol
Acidity (pKa) 2.46, 7.3[2]
Related compounds
Other anions
selenic acid
hydrogen selenide
Other cations
sodium selenite
Related compounds
sulfurous acid
tellurous acid
polonous acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 Y  (: Y/N?)

Selenous acid (or selenious acid) is the chemical compound with the formula H2SeO3. Structurally, it is more accurately described by (HO)2SeO. It is the principal oxoacid of selenium; the other being selenic acid.

Contents

  • Formation and properties 1
  • Uses 2
  • Health effects 3
  • References 4

Formation and properties

Selenous acid is analogous to sulfurous acid, but it is more readily isolated. Selenous acid is easily formed upon the addition of selenium dioxide to water. As a crystalline solid, the compound can be seen as pyramidal molecules that are interconnected with hydrogen bonds. In solution it is a diprotic acid:[3]

H
2
SeO
3
H+
+ HSeO
3
(pKa = 2.62)
HSeO
3
H+
+ SeO2−
3
(pKa = 8.32)

It is moderately oxidizing in nature, but kinetically slow. In 1 M H+
:

H
2
SeO
3
+ 4 H+
+ 4 e Se + 3 H
2
O
(Eo = +0.74 V)

In 1 M OH
:

SeO2−
3
+ 4 e + 3 H
2
O
Se + 6 OH
(Eo = −0.37 V)

It is used in ketones (e.g. glyoxal).[4]

Uses

The major use is in changing the color of steel, especially the steel in guns, the so-called "bluing" process which uses selenous acid, copper(II) nitrate, and nitric acid to change the color of the steel from silver-grey to blue-grey. Some older razor blades were also made of blued steel.[5]

Another use for selenious acid is the chemical darkening and patination of copper, brass and bronze, producing a rich dark brown color that can be further enhanced with mechanical abrasion.

Selenious acid is a key component of the Mecke reagent used for drug testing.[6]

Health effects

Like many selenium compounds, selenous acid is highly toxic in excessive quantities, and ingestion of any significant quantity of selenous acid is usually fatal, however it is an approved dietary source in proper amounts. Symptoms of selenium poisoning can occur several hours after exposure, and may include stupor, nausea, severe hypotension and death.[7]

References

  1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–81.  
  2. ^ http://www2.ucdsb.on.ca/tiss/stretton/database/polyprotic_acids.htm
  3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  4. ^ “Glyoxal Bisulfite”, Organic Syntheses, Collected Volume 3, p.438 (1955).
  5. ^ Scarlato, E.A.; Higa, J. (28 June 1990). USES/HIGH RISK CIRCUMSTANCES OF POISONING "SELENIUM" . Retrieved 29 December 2010. 
  6. ^ "Colour Test Reagents-Kits for Preliminary Identification of Drugs of Abuse" (PDF). National Institute of Justice. 2000-07-01. Retrieved 2012-01-26. 
  7. ^ MSDS for "Reagent for Special Opiates (Codeine, Heroin, & Morphine)", Sirchie Finger Print Laboratories, Inc. May 12, 2006. (The page cannot be found)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.