Cobalt arsenides

Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003% of the Earth s crust. It is not found in the free metallic state, despite being widely distributed in igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) and erythrite [Co lAsO l ]. These ores are placed in blast furnaces to produce cobalt arsenide (COjAs), which is then treated with sulfuric acid to remove the arsenic. Finally, the product cobalt tetraoxide (Co O ) is reduced by heat with carbon (Co O + C — 3Co + 2COf resulting in cobalt metal. 

Cobalt Arsenides.—Cobalt alloys readily with arsenic and several compounds have been prepared. On the freezing point curve5 there is a eutectic point at 916° C. and 30 per cent. As, and maxima occur at 926° C., 959° C. and 1180° C., corresponding respectively with Co6As2 (33-7 per cent. As), Co2As (38-9 per cent. As) and CoAs (about 55 per... 

Cobalt Arsenide or Cobalt Monarsenide, CoAs, is obtained when the previous compound is heated from 600-800° C., and when cobalt is heated to 275-335° C. in arsenic vapour. It is a grey crystalline powder, of density 7-62, which tarnishes slightly in the air.1... 

Skutterudite Cobalt arsenide (Ni, Co) As 3 White to silver. Metallic Black 6 6.5 6.8... 

Badham J. P. N. Orogenesis and metallogenesis with reference to the silver-nickel, cobalt arsenide ore association. In Metallogeny and plate tectonics Strong D. F. ed. Spec. Pap. geol. Ass. Can. 14, 1976, 560-71. 

---