Chemical Properties

Cobalt is somewhat of a reactive element. It combines with oxygen in the air, but does not catch on fire and burn unless it is in powder form. Cobalt has the ability to react with most acids to produce hydrogen gas. However cobalt does not react with water that is at room temperature. The simplest ion that cobalt forms in solution is the pink hexaaquacobalt(II) ion - [Co(H₂O)₆]²⁺. Cobalt(II) chloride is often used in humidity indicators because in dry form it is blue and when hydrated it is pink. The radioactive isotope of cobalt, Co-60, is used in portable "x-ray" devices. It actually produces gamma rays which can be used to detect internal flaws in metal in much the same way as x-rays by producing a shadowy image on film. Co-60 is also used in cancer treatment.