Inhale Lately?
(WebElements.com)
CHROMIUM
(WebElements.com)
Physical:
Atomic number: 24
Mass: 51.9961
Melting Point: 1860 °C (3380 °F)
Boiling Point: 2670 °C (4838 °F)
No taste or odor
(periodictable.com)
Chemical:
Oxidation states
Common: +2, +3, +6
Rare: +1, +4, +5
Cr III – Most stable
insoluble in water
Cr VI – prevails in seawater
100 – 1000x more toxic
Isotopes
*3 stable isotopes
52Cr, 53Cr, and 54Cr
*19 radioisotopes
most stable being 50Cr
with half life > 1.8 x 1017 years
51Cr
half life 27.7 days
Rest have half life <24 hours
majority < 1 minute
Uses
*Trace element for glucose metabolism
not found as free metal in nature
found as Chromite FeCr2O4
& Crocoite PrCrO4
Abundantly found in the Earth’s crust
*Industrial uses:
protective coating on metal, stainless steel, magnetic tapes,
pigments in paints, cement, paper, rubber & floor coverings
wood preservatives, tanning leather, fungicides,
green color of emeralds, red color of rubies
How do they use it?
Oil paints use Crocoite (Siberian red lead) – PrCrO4
Commercially – alter Chromite ore Fe Cr2O4
oxidation by air  Na2CrO4 (can continue to 6+ state)
extraction into water  Cr(III) oxide: Cr2O3
Reacts with other elements
Cr2O3 + 2Al  2Cr + Al2O3
2Cr2O3 + 3Si  4Cr + 3 SiO2
Chromium meet Environment
Introduced to air, soil and water
*Manufacturing: chemical, pharmaceutical, metal finishes,
paint dyes
manufacturing releases hexavalent chromium (Cr+6)
*Disposal of Products or Chemicals containing Cr
*Burning of Fossil Fuels
*Welding on stainless steel
*Melting Cr metal
Cr settles from air within 10 days
sticks strongly to soil particles.
Toxicity of Cr
Cr III – moderate acute toxicity to aquatic life
Cr III & Cr VI – high chronic toxicity to aquatic life
LC50: Fish – 7-400 ppm
Daphnia – 001-0.26 ppm
Algae – 0.032 – 6.4 ppm
Inhibits photosynthesis for aquatic plants
reduces photo pigments, proteins, cysteine, ascorbic acid
and non-protein thiol.
In aquatic animals
leads to metabolic issues, damage to liver, kidney and
nerve tissue. Can cause lung cancer in some mammals.
Toxicity defense: Increase superoxide dismutase, guaiacol,
peroxidase and catalase
Alter metabolic processes
References
Chaudhary, S, Van Horn, J.D. (2007) Breakdown Kinetics of the tri-chromium (III)
oxo acetate cluster ( [Cr3O(OAc)6]+ with some ligands of biological interest.
Journal of Inorganic Biochemistry 101 (2): 329-335
Department of the Environment, Water, Heritage and the Arts. (2008) Austrailian
Government. Accessed April 23, 2008 <www.npi.gov.au>
Horcsik, ZT et al (2007) Effetcs of chromium on photosystem 2 in the unicellular
green algae, Chlorella pyrenoidasa. Photosynthetica 45 (1): 65-69
Mathematica (2008) Wolfram research. Accessed April 23, 2008.
<www.periodictable.com>
Rai, V et al (2004) Effect of chromium accumulation on photosynthetic pigments,
oxidative stress defense system, nitrate reduction, proline level and eugenol
content of Ocimum tenuiflorum. Plant Science 167 (5): 1159-1169
Winter, Mark (2008) University of Sheffield. Accessed April 23, 2008.
<www. Webelements.com
Questions?
(webelements.com)