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.

Synthesis

Nickel(II) chromate can be formed in the lab by heating a mixture of chromium(III) oxide and

nickel oxide Nickel oxide may refer to: * Nickel(II) oxide, NiO, green, well-characterised oxide * Nickel(III) oxide Nickel (III) oxide is the inorganic compound with the formula Ni2O3. It is not well characterized, and is sometimes referred to as black nic ...

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. If the pressure is too low or temperature too high but above 660 °C, then the nickel chromium

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties S ...

NiCr₂O₄ forms instead. Karin Brandt also claimed to make nickel chromate using a hydrothermal technique. Precipitates of Ni²⁺ ions with chromate produce a brown substance that contains water.

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. Nickel chromate is dark in colour, unlike most other chromates which are yellow. 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.

Reaction

When heated at lower oxygen pressure around 600 °C, nickel chromate decomposes to the nickel chromite spinel, nickel oxide and oxygen. :4 NiCrO₄ → 2 NiCr₂O₄ + 2 NiO + 3 O₂ (gas)

Nickel chromates can also crystallize with ligands. For instance, with

1,10-phenanthroline 1,10-Phenanthroline (phen) is a heterocyclic organic compound. It is a white solid that is soluble in organic solvents. The 1,10 refer to the location of the nitrogen atoms that replace CH's in the hydrocarbon called phenanthrene. Abbreviated ...

it can form triclinic olive-colored crystals of i(1,10-phenanthroline)CrO₄•3H₂O��H₂O, orange crystals of Ni(1,10-phenanthroline)₃Cr₂O₇•3H₂O, and yellow powdered Ni(1,10-phenanthroline)₃Cr₂O₇•8H₂O.

References

{{Chromates and dichromates Nickel compounds Chromates Oxidizing agents

Synthesis

Properties

Reaction

Related

References