Inhale Lately? (WebElements.com)
CHROMIUM (WebElements.com) (periodictable.com) Physical: Chemical: Oxidation states Common: +2, +3, +6 Rare: +1, +4, +5 Atomic number: 24 Mass: 51.9961 Melting Point: 1860 °C (3380 °F) Boiling Point: 2670 °C (4838 °F) Cr III – Most stable insoluble in water No taste or odor 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