Cobalt(II) oxide
Cobalt(II) oxide (CoO) is a grayish green cobalt compound used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical production industry for producing cobalt(II) salts.
Cobalt(II) oxide is a product of Cobalt(II,III) oxide decomposing at 895 °C through the reaction:
- 2 Co3O4(s) → 6 CoO(s) + O2(g)
Cobalt(II) oxide is also a product of Cobalt(II) carbonate decomposing when heated through the reaction:
- CoCO3(s) → CoO(s) + CO2(g)
Recent research also indicates that through the vaporization of metallic cobalt by the use of a laser in a process known as LVCC or (Laser Vaporization Controlled Condensation) in an environment of N2 and O2 gases. The proportion of nitrogen to oxygen gas will determine the resulting product, for example, a 1:1 mixture will yield a product consisting mostly of cobalt(II) nitrate instead of the oxide [1].
Ceramics and Other Uses
Cobalt(II) oxide has been used for centuries as a coloring agent on kiln fired ceramic glazes, the earliest examples go back to the beginnings of kiln fired pottery. Cobalt(II) oxide colorants are stable and retain their coloration indefinitely. The oxide is one of the most powerful colorants commonly used in the making of glazes and slips and requires only 1 part oxide to 100,000 parts glazing compound to produce the deep blue shade commonly referred to as cobalt blue. By varying the temperature of the kiln, the potter can adjust the coloring of the oxide ranging anywhere from the familiar blue, to a darker shade nearing black. [2] Cobalt(II) oxide is also used in dryers used with oil based paints to expedite their curing. These substances can be found at most art stores.
Industrial Uses
As stated earlier, cobalt(II) oxide is used in the production of cobalt(II) salts such as CoCl2 and Co(NO3)2. Cobalt(II) oxide is also found in animal feed and fertilizer as a supplement to aid in the production of Vitamin B12, or cobalamin.
Health Concerns
This oxide is also found in cobalt dryers, additives to paints that can be found at most art stores. These dryers are considered highly toxic and a "possible human carcinogen" by the International Agency for Research on Cancer. Symptoms of acute exposure include coughing, wheezing and difficulty breathing. The small particles also pose the risk of ocular inflammation. The use of NFPA/NIOSH approved respiratory equipment is recommended when handling this substance.[3] OSHA's established exposure limit is 0.1 milligrams per cubic foot of air per 8 hour period. [4]
Toxicology
LD50/LC50 tests indicate that in rats a dose of 202mg per kilogram given orally is fatal. In 1992 the State of California added Cobalt(II) oxide to its list of carcinogenic agents however RTECS does not officially list the oxide as a carcinogen.[5]
Reactivity Concerns
Cobalt(II) oxide rapidly decomposes hydrogen peroxide and oxidizes the drying of unsaturated oils in an exothermic reaction that can be potentially explosive. [6]
References
- ↑ Garry P. Glaspell, Paul W. Jagodzinski and A. Manivannan: "Formation of Cobalt Nitrate Hydrate, Cobalt Oxide, and Cobalt Nanoparticles Using Laser Vaporization Controlled Condensation" April 13th 2004 <http://pubs.acs.org/cgi-bin/abstract.cgi/jpcbfk/2004/108/i28/abs/jp0370831.html>
- ↑ Zamek, Jeff: "A Problem With Cobalt?" Ceramics Today <http://www.ceramicstoday.com/articles/zamek_cobalt.htm>
- ↑ American Chemical Society: "Journal of Chemical Education" Vol.28 No. 10 October 2001 "Hazardous Characteristics" <http://membership.acs.org/c/ccs/pubs/CLIPS/JCE20011328.pdf>
- ↑ Occupational Safety and Health Administration: "Cobalt Metal, Dust, and Fume" <http://www.osha.gov/SLTC/healthguidelines/cobaltmetaldustandfume/recognition.html> 22 April 1999
- ↑ Fisher Scientific UK MSDS "Cobalt(II) oxide" § 11 'Toxicological Information'
- ↑ American Chemical Society: "Journal of Chemical Education" Vol.28 No. 10 October 2001 "Hazardous Characteristics" <http://membership.acs.org/c/ccs/pubs/CLIPS/JCE20011328.pdf>