1854. KINCAID, J. F., AND STRONG, J. S. (Rohm & Haas Co.). Nickel Carbonyl. United States Patent 2,548,727, Apr. 10, 1951. Chem. Abs., vol. 45, 1951, p. 6357.

Ni (CO)₄ is made by treating a fluid aqueous slurry of freshly precipitated

Ni (OH)₂ (0.1-1.5 moles per 1. of slurry) containing a small amount of a complex mixture of S compounds, for example Na₂S or Na₂S₂O₃ (4-12 mole %, based on Ni salt), with CO at 60°-200° under a pressure in excess of 1,000 p. s. i. and under alkaline conditions. The Ni (OH)₂ is first prepared by mixing in H₂O a water-soluble Ni salt, for example NiCl₂ or NiSO₄, and an alkali or alkaline earth hydroxide, for example NaOH, KOH, or Ca (OH)₂. Over 99% conversion of Ni to Ni (CO)₄ is obtained in about 1 hr.