It is readily soluble in warm dilute mineral acids forming cobaltous salts.
They are formed by the action of nitrous fumes on ammoniacal solutions of cobaltous salts, or purpureo-salts, or by the mutual reaction of chlorpurpureosalts and alkaline nitrites.
Cobaltous hydroxide, Co(OH) 21 is formed when a cobaltous salt is precipitated by caustic potash in the absence of air.
The pentammine roseo-salts can be obtained from the action of concentrated acids, in the cold, on airoxidized solutions of cobaltous salts.
Cobalt dioxide, Co02, has not yet been isolated in the pure state; it is probably formed when iodine and caustic soda are added to a solution of a cobaltous salt.
Cobaltic hydroxide, Co(OH) 31 is formed when a cobalt salt is precipitated by an alkaline hypochlorite, or on passing chlorine through water containing suspended cobaltous hydroxide or carbonate.
The cobaltous salts are formed when the metal, cobaltous oxide, hydroxide or carbonate, are dissolved in acids, or, in the case of the insoluble salts, by precipitation.
The diammine salts are prepared by the action of alkaline nitrites on cobaltous salts in the presence of much ammonium chloride or nitrate; they are yellow or brown crystalline solids, not very soluble in cold water.
Cobaltous sulphate, CoSO 4.7H 2 O, is found naturally as the mineral bieberite, and is formed when cobalt, cobaltous oxide or carbonate are dissolved in dilute sulphuric acid.
For the action of ammonia on the cobaltous salts in the presence of air see Cobaltammines (below).