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Physical & Chemical properties

Water solubility

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The water solubility of green nickel oxide has been determined to be 2.71 x 10-5 g/l of solution at 20.0 ± 0.5°C monitoring nickel; equivalent to 3.52 x 10-5 g/l of test material.  The water solubility of black nickel oxide was found to be 2.26 x 10-3 g/l of solution.  Both analyses were based on theoretical nickel content using the flask method, Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 105 of the OECD Guidelines for Testing of Chemicals, 27 July 1995.  
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 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]. 8th ed. Verlag Chemie.
Van Vlack, L. 1980. The oxides of nickel. International Nickel Company, Inc.

Key value for chemical safety assessment

Water solubility:
0 g/L
at the temperature of:
20 °C

Additional information