Nickel(II) chromate

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Nickel chromate
Names
IUPAC name
Nickel(II) chromate
Other names
nickelous chromate
nickel chromate
nickel(II) chromium(VI) oxide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.035.227 Edit this at Wikidata
EC Number
  • 238-766-5
  • InChI=1S/Cr.Ni.4O/q;+2;;;2*-1
    Key: QGAXAFUJMMYEPE-UHFFFAOYSA-N
  • [O-][Cr](=O)(=O)[O-].[Ni+2]
Properties
NiCrO4
Molar mass 174.71 g/mol
Appearance dark maroon-colored powder
very slightly soluble in water[1]
Solubility soluble in hydrochloric acid
Hazards
Flash point Non-flammable
Related compounds
Other anions
 nickel(II) molybdate
nickel(II) tungstate
Other cations
 magnesium chromate
cadmium chromate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Nickel(II) chromate (NiCrO4) is an acid-soluble compound, red-brown in color, with high tolerances for heat. It and the ions that compose it have been linked to tumor formation and gene mutation, particularly to wildlife.[2]

Synthesis

Nickel(II) chromate can be formed in the lab by heating a mixture of chromium(III) oxide and nickel oxide at between 700 °C and 800 °C under oxygen at 1000 atm pressure. It can be produced at 535 °C and 7.3 bar oxygen, but the reaction takes days to complete.[3] If the pressure is too low or temperature too high but above 660 °C, then the nickel chromium spinel NiCr2O4 forms instead.[3]

Karin Brandt also claimed to make nickel chromate using a hydrothermal technique.[4][5]

Precipitates of Ni2+ ions with chromate produce a brown substance that contains water.[6]

Properties

The structure of nickel chromate is the same as for chromium vanadate, CrVO4. Crystals have an orthorhombic structure with unit cell sizes a = 5.482 Å, b = 8.237 Å, c = 6.147 Å. The cell volume is 277.6 Å3 with four formula per unit cell.[5][7]

Nickel chromate is dark in colour, unlike most other chromates which are yellow.[3] The infrared spectrum of nickel chromate show two sets of absorption bands. The first includes lines at 925, 825, and 800 cm−1 due to Cr-O stretching, and the second has lines at 430, 395, 365 (very weak) due to Cr-O rock and bend and 310 cm−1 produced from Ni-O stretching.[8]

Reaction

When heated at lower oxygen pressure around 600 °C, nickel chromate decomposes to the nickel chromite spinel, nickel oxide and oxygen.[3]

4 NiCrO4 → 2 NiCr2O4 + 2 NiO + 3 O2 (gas)

Related

Nickel chromates can also crystallize with ligands. For instance, with 1,10-phenanthroline it can form triclinic olive-colored crystals of [Ni(1,10-phenanthroline)CrO4•3H2O]•H2O, orange crystals of Ni(1,10-phenanthroline)3Cr2O7•3H2O, and yellow powdered Ni(1,10-phenanthroline)3Cr2O7•8H2O.[6]

References

  1. ^ Perry, Dale L. (19 April 2016). Handbook of Inorganic Compounds, Second Edition. CRC Press. p. 290. ISBN 9781439814628.
  2. ^ Eisler, R. (1998). Nickel Hazards to Fish, Wildlife, and Invertebrates: a Synoptic Review. Laurel: U.S. Geological Survey
  3. ^ a b c d Muller, Olaf; Roy, Rustum; White, William B. (December 1968). "Phase Equilibria in the Systems NiO-Cr2,O3,-O2, MgO-Cr2O3-O2, and CdO-Cr2,O3,-O2, at High Oxygen Pressures". Journal of the American Ceramic Society. 51 (12): 693–699. doi:10.1111/j.1151-2916.1968.tb15930.x.
  4. ^ Brandt, Karin (1943). "X-Ray Analysis of CrVO4 and isomorphous compounds". Arkiv för Kemi, Mineralogi och Geologi. 17A (6): 1–13. (not consulted)
  5. ^ a b Muller, Olaf; White, William B.; Roy, Rustum (September 1969). "X-ray diffraction study of the chromates of nickel, magnesium and cadmium". Zeitschrift für Kristallographie. 130 (1–6): 112–120. Bibcode:1969ZK....130..112M. doi:10.1524/zkri.1969.130.1-6.112.
  6. ^ a b Bronowska, W; Staszak, Z; Daszkiewicz, M; Cieślak-Golonka, M; Wojciechowska, A (May 2002). "Systematic investigation of the [Ni2+–phen–CrO42−] system; dichromate species isolated from alkaline solutions". Polyhedron. 21 (9–10): 997–1003. doi:10.1016/S0277-5387(02)00912-9.
  7. ^ Baran, E. J (May 1998). "Materials belonging to the CrVO4 structure type: preparation, crystal chemistry and physicochemical properties". Journal of Materials Science. 33 (10): 2479–2497. Bibcode:1998JMatS..33.2479B. doi:10.1023/A:1004380530309. S2CID 97516785.
  8. ^ Muller, Olaf; White, William B.; Roy, Rustum (August 1969). "Infrared spectra of the chromates of magnesium, nickel and cadmium". Spectrochimica Acta Part A: Molecular Spectroscopy. 25 (8): 1491–1499. Bibcode:1969AcSpA..25.1491M. doi:10.1016/0584-8539(69)80133-9.
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