2304.     MOND, L., HIRTZ, H., AND COWAP, M. D.  Note on a Volatile Compound of Cobalt With Carbon Monoxide.  Chem. News, vol. 98, 1908, p. 165; Chem. Abs., vol. 2, 1908, p. 3315.

        Finely divided Co and CO at 150° and under 50 atm. yielded small quantities of Co carbonyl; at 200° under 100 atm. the yield was higher.  The Co was prepared by converting CoC₂O₃, free from Ni and Fe, to oxide, and reducing the latter to metal with H₂ in the retort used for the production of the carbonyl.  The carbonyl was obtained in large orange crystals, agreeing in composition with the formula Co(CO)₄.  It decomposes in air to a violet substance, as yet uninvestigated, and is best preserved by sealing up in H₂ or CO.  It is but slowly attacked by nonoxidizing acids but very readily by oxidizing agents, for example, Co(CO)₄+Br₂→CoBr₂+4CO.  It is insoluble in N₂O but more or less soluble in CS₂, ether, naphtha, alcohol, and Ni carbonyl.  If these solutions stand for some time or are warmed, decomposition sets in, D₁₈1.827; vapor tension at 15°, 11 mm.  Both of these values, however, are affected by the ease with which the carbonyl decomposes and are not to be regarded as final.  In an atmosphere of CO₂, the decomposition begins at 40°-45° and is complete at 130°-135°, leaving metallic Co.  The melting point is 42°-46°.