Cobalt. CO; at. wt. 58.94; at. no. 27; valence 2-3.

Discovered in 1735 by Brandt.

Gray, hard, magnetic, ductile, somewhat

malleable metal. Crystallizes in hexagonal or cubic form. Stable in air or toward water at ordinary temp. d. 8.9. m. 1480°. b. 2900°. Brinell hardness = 125. Readily soluble in dil. HNO₃; very slowly attacked by HCI or cold H₂SO₄.

The hydrated salts of cobalt are red, and the soluble salts form red solns. which become blue on adding concentr. HCl.

Use: For alloys; manuf. cobalt salts. Commercially available.

Toxicity: Inhalation of dust may cause pulmonary symptoms. Powder may cause dermatitis.

Max. allowable concn. reported to be 0.5 mg./cu. m. of air. Ingestion of soluble salts produces nausea and vomiting by local irritation.

{Mineral Deficiencies in Plants}