Chemical elements
    Physical Properties
      Nickel Fluoride
      Nickel Dichloride
      Double Nickel Chlorides
      Nickel Dibromide
      Nickel Di-iodide
      Nickel Chlorate
      Nickel Perchlorate
      Nickel Bromate
      Nickel Iodate
      Tri-nickel Suboxide
      Nickel Suboxide
      Nickel Monoxide
      Nickel Dihydroxide
      Nickelo-nickelic Oxide
      Nickel Dioxide
      Nickel Subsulphide
      Nickel Monosulphide
      Nickel Sesquisulphide
      Tri-nickel Tetrasulphide
      Nickel Disulphide
      Nickel Tetrasulphide
      Nickel Sulphite
      Nickel Thiosulphate
      Nickel Dithionate
      Nickel Sulphate
      Nickel Subselenide
      Nickel Selenide
      Nickel Sesquiselenide
      Nickel Selenite
      Nickel Sesquitelluride
      Nickel Tellurite
      Nickel Chromate
      Nickel Dichromate
      Double Nickel Chromates
      Nickel Molybdate
      Nickel Nitride
      Nickel Azoimide
      Nickel Nitrite
      Nickel Nitrate
      Di-nickel Phosphide
      Nickel Sesquiphosphide
      Nickel Diphosphide
      Nickel Triphosphide
      Nickel Hypophosphite
      Nickel Phosphite
      Nickel Metaphosphate
      Nickel Orthophosphate
      Nickel Pyrophosphate
      Nickel Thio-orthophosphate
      Nickel Thiopyrophosphite
      Nickel Thiopyrophosphate
      Tri-nickel Diarsenide
      Nickel Arsenide
      Nickel Diarsenide
      Nickel Arsenite
      Nickel Orthoarsenate
      Nickel Antimonide
      Nickel Antimonate
      Nickel Thioantimonite
      Nickel Vanadate
      Nickel Carbide
      Nickel Tetracarbonyl
      Nickel Carbonate
      Nickel Monocyanide
      Nickel Cyanide
      Nickel Thiocyanate
      Nickel Thiocarbonate Hexammoniate
      Nickel Subsilicide
      Nickel Orthosilicate
      Nickel Monoboride
      Nickel Borates
    PDB 1a5n-1g2a
    PDB 1g3v-1mn0
    PDB 1mro-1s9b
    PDB 1scr-1xmk
    PDB 1xu1-2cg5
    PDB 2cqz-2jih
    PDB 2jk8-2v4b
    PDB 2vbq-3c2q
    PDB 3c6c-3h85
    PDB 3hdp-3kvb
    PDB 3l1m-3o00
    PDB 3o01-4ubp
    PDB 8icl-9ant

Nickel Monoxide, NiO

Nickelous Oxide or Nickel Monoxide, NiO, occurs in nature as the mineral Bunsenite in regular octahedra, of density 6.4. In the laboratory it may be obtained by heating the hydroxide, sesqui-oxide, nitrate, or carbonate, when it results as a green crystalline powder, which, on heating, assumes a deep yellow colour. When nickel is heated in steam to a dull red heat, or in nitric oxide to at least 200° C., nickelous oxide is formed. The oxide may also be prepared by igniting nickel borate and lime at a high temperature, and separated as green crystals by treating the cooled mass with aqueous hydrogen chloride. Its density ranges from 6.6 to 6.8.

Nickelous oxide may be reduced more or less completely to the metallic condition by heating in a current of hydrogen at 220° C., in carbon monoxide at 120° C., and in ammonia above 200° C. Solid carbon reduces it at 450° C. These temperatures of reduction, however, depend upon the mode of preparation and subsequent chemical history of the oxide. Below 300° C. reduction is not complete, but the product- is very active catalytically.

When ignited in air, nickelous oxide absorbs oxygen, but loses it again as the temperature is raised. When prepared by ignition of nickel nitrate, the oxide contains occluded oxygen and nitrogen, the latter gas predominating.

In the electric furnace it melts and on cooling solidifies to green crystals. By repeated heating to 1000° C. in excess of potassium chloride, amorphous nickel monoxide yields minute octahedral crystals, light yellowish green in colour, and of density 7.45. It becomes incandescent in fluorine, and in hydrogen sulphide yields an oxysulphide, 2NiS.NiO. Acids dissolve it, yielding nickel salts.

Nickel oxide unites with oxides of several other metals to yield crystalline substances of varied composition. With alumina a blue aluminate, NiO. Al2O3, is obtained by fusing the two oxides together at 900° C., using potassium chloride as a flux. It crystallises in small octahedra or octahedral cubes, and even a small excess of either oxide can be distinguished microscopically. With manganese oxide, series of homogeneous mixed crystals have been obtained in an analogous manner, with compositions ranging from NiO.5MnO to 5NiO.MnO. The crystals are slightly yellowish green in colour, and form octahedra and octahedral cubes.

The oxides of magnesium, zinc, and tin likewise yield interesting mixtures.

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