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Physical & Chemical properties

Endpoint summary

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The NiO representative sample (green nickel oxide) was used to generate data for all relevant endpoints and the results are provided in the associated study records and endpoint summaries for all relevant physical and chemical properties endpoints. However, for one endpoint (water solubility), data were generated for both green nickel oxide and black nickel oxide. Data for several endpoints were waived based on appropriate justifications provided in the relevant endpoint summaries and study records. There are no classifications for physico-chemical properties.

Please note that nickelous oxide, NiO, exists as a large group that includes a continuous spectrum of compounds from a high-temperature, green variety to a low-temperature, jet-black product.  Only stoichiometric NiO comes in the form of transparent green crystals.  Thermal history of NiO formation, which usually involves calcination of a nickel compound such as hydroxycarbonate, hydroxide, sulfate, nitrate, oxalate, or sulfide, as well as oxidation of a pure nickel metal powder, is the main factor which determines the color, chemical reactivity, and the stoichiometric proportions of nickel and oxygen in the resulting oxide (Gmelin 1966; Van Vlack, 1980). The physicochemical properties described in the table below apply to both the low calcining temperature (black) and the high calcining temperature (green) forms of nickel oxide. Experts with specific knowledge on oxidic nickel compounds agree that the main chemical properties where differences between these forms are expected are water solubility and solubility in acids (B. Conard, PhD and W. Ghyoot, PhD, personal communication). Water solubility values are shown separately for the low calcining temperature (black) and the high calcining temperature (green) forms of nickel oxide.

Gmelin. 1966. Gmelins Hanbuch der anorganischem Chemie [Gmelins handbook of inorganic chemistry]. 8thed.,: Verlag Chemie.

Van Vlack, L. 1980. The oxides of nickel.,: International Nickel Company, Inc.