1. Nickel carbonyl is a highly toxic compound.2. Dissociation of nickel carbonyl takes place rapidly at the temperature of the body in the presence of air, moisture and carbon dioxide.Nickel carbonyl also dissociates at the temperature of the body in the absence of air, moisture and carbon dioxide, but not to the same extent as in the presence of these owing to the fact that a reversible action occurs between the nickel and the dissociated carbon monoxide.3. Nickel carbonyl is soluble in water to the amount of 2·36 c.cm. of vapour (i.e. 6·43 mgrs. of nickel) per 100 grs. at 9·8° C.The amount dissolved in water is directly proportional to the pressure, when the temperature is constant.The solubility in water diminishes as the temperature is raised.4. The solubility of nickel carbonyl in serum and in blood is about 2½ times greater than that in water. At 10° C. 100 grs. of serum dissolves 5·98 c.cm. of nickel carbonyl vapour (i.e. 15·71 mgrs. of nickel).5. When nickel carbonyl is brought into contact with water, serum, blood and other liquids, if oxygen and carbon dioxide are present, dissociation occurs and a substance is formed, probably a hydrated basic carbonate of nickel, which is slightly soluble, but also forms a very fine precipitate, which renders the liquid turbid. The liquid can only be cleared of the turbidity by passing it through a Berkefeld filter.6. Water dissolves about 0·0035% of the product of dissociated nickel carbonyl (reckoned as nickel) at 18° C. About the same amount is dissolved in 10% solutions of sodium carbonate.The solubility of this product of dissociated nickel carbonyl is greater in serum than in water. Serum dissolves about 0·0183% (reckoned as nickel). A solution of the salts of serum, under the same conditions, dissolves 0·005% (reckoned as nickel). Solutions of sodium phosphate of approximately the same strength as the phosphates in serum, dissolve 0·0025% (reckoned as nickel).7. Nickel hydrate is insoluble in water but is soluble in serum to the extent of 0·0225 gr. nickel per 100 grs. serum, and in sodium phosphate solutions to the extent of 0·012% (reckoned as nickel).8. Nickel carbonate is soluble in water to the extent of 0·0005% (reckoned as nickel), and in serum to an amount, corresponding to 0·016 gr.% of nickel. Salts of serum dissolve 0·0045 gr. % of nickel carbonate reckoned as nickel. Nickel carbonate is insoluble in sodium phosphate solutions.9. Dissociation product in aqueous solution is precipitated by boiling, and to a certain extent by the addition of electrolytes. Some of it is thrown out of solution spontaneously on standing for some days, whereas solutions of nickel carbonate are not precipitated by either of the above means.10. Solutions of dissociation product dialyse more slowly than solutions of similar strength of nickel carbonate, and at a certain stage in the dialysis the greater part of the nickel is adsorbed into the membrane.11. No constant ratio exists between the nickel and the nitrogen contents of solutions of dissociation product in serum of different strengths.12. When the proteids of the serum, containing the product of dissociated nickel carbonyl in solution, are precipitated by ammonium sulphate, nine-tenths of the nickel remains in solution. One-tenth is precipitated by adding sufficient ammonium sulphate to produce one-third of saturation, and about an additional one-hundredth by producing one-half of saturation.13. The product of dissociated nickel carbonyl when dissolved in serum is only incompletely removable from solution by dialysis.The product of dissociated nickel carbonyl is therefore not identical with nickel carbonate or nickel hydrate, and appears to exist in a condition of colloidal solution.14. The poisonous properties of nickel carbonyl do not depend, as was at first supposed, on the carbon monoxide of the compound.15. Nickel carbonyl when mixed with air and inhaled by an animal, cannot be absorbed as such, as it becomes split up into the nickel containing substance (? hydrated basic carbonate of nickel) and carbon monoxide, before or soon after reaching the alveoli of the lungs.16. The poisonous effects of nickel carbonyl are entirely due to the nickel of the compound. The peculiar toxicity of the compound is due to the fact that being introduced in a gaseous form and that the nickel is deposited as a slightly soluble compound in a very fine state of subdivision over the immense area of the respiratory surface.
