|Molar mass||165.39 g/mol|
|Appearance||black-dark gray solid|
600 °C (decomposes)
|Solubility in water||negligible|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Nickel(III) oxide (Ni2O3) has been referred to in the literature, but is not a well characterised compound. The substance black nickel oxide is sometimes described as being Ni2O3; however, the composition quoted by suppliers has a nickel content of around 77% by weight, whereas Ni2O3 would have 70.98% Ni by weight, and may be non-stoichiometric NiO.
There are references in the literature to traces of Ni2O3 on nickel surfaces, and as intermediates in nickel oxidation, e.g.
Nickel oxide hydroxide 
4OH- + 2NiCl2 + NaClO ---> Na+ + H2O + 2NiOOH + 5Cl-
or in double oxidation of 3-butenoic acid to fumaric acid:
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.
- An oxide of tervalent nickel , P. S. Aggarwal, A. Goswami, J. Phys. Chem.; 1961; 65(11); 2105-2105, doi:10.1021/j100828a503
- Chemical vapor deposition of nickel oxide films from Ni(C5H5)2/O2, Jin-Kyu Kang, Shi-Woo Rhee, Thin Solid Films, 391, 1, (2001),57-61, doi:10.1016/S0040-6090(01)00962-2
- An Efficient and Practical System for the Catalytic Oxidation of Alcohols, Aldehydes, and ,-Unsaturated Carboxylic Acids Joseph M. Grill, James W. Ogle, and Stephen A. Miller J. Org. Chem.; 2006; 71(25) pp 9291 - 9296; (Article) doi:10.1021/jo0612574