title: Influence of physicochemical properties, methods of preparation and purity of nickel compounds on their biological effects.
abstract: Epidemiological investigations carried out on workers in certain areas of nickel refineries have shown that a relationship exists between exposure to certain nickel compounds and cancer of the nasal passages and the lungs. Animal experiments have shown that nickel compounds cause tumours, the carcinogenicity being greater the lower the solubility of the compound in water (solubility less than 10(-3) mole/l). Amorphous nickel monosulfide (solubility less than 10(-5) mole/l) is an exception to this rule. It has been demonstrated by X-ray photoelectron spectroscopy that the surface properties of crystalline nickel monosulfide differ from those of the amorphous variety, in that amorphous nickel monosulfide has a positive surface charge while that of the crystalline sulfide is negative. It would seem that, as in the case of asbestos, a negative surface charge is an important factor in the ability to transform cells. Carcinogens are electrophiles. The differences in the behaviour of nickel compounds can be explained by the theory of hard and soft acids and bases. These considerations and the differences in the rates of cell transformation show the importance of the methods used to prepare the compounds (precipitation from solution, reaction between the elements in vacuo, solid-gas reactions) which very often lead to the formation of non-stoichiometric phases (hexagonal nickel monosulfide, nickel monoxide, high-temperature nickel subsulfide) having completely different thermodynamic, electrical, magnetic and surface properties and specific surface areas. Phase and Eh pH diagrams as well as those of Ellingham (1948) for the nickel oxides and sulfides show that certain phases are unstable and that it is important to specify precisely the conditions governing storage, grinding, handling and injection. A precise knowledge is required of the chemical composition of ores, mattes and dusts, since certain elements and compounds, e.g., manganese, even when present only in trace amounts, can act either as promoters or inhibitors in biological processes. This paper therefore demonstrates the importance of specifying the methods of preparation and determining the physico-chemical properties and purity of nickel compounds before biological studies are undertaken.
mesh_terms: D002273:Carcinogens; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006801:Humans; D008669:Metallurgy; D009532:Nickel; D012995:Solubility; D013455:Sulfur; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002273:Carcinogens; D013455:Sulfur; D009532:Nickel