Cobalt;sulfuric acid

UsesCobalt(II) sulfate is used in storage batteries and electroplating baths for cobalt. It also is used as a dryer for lithographic inks; in pigments for decorating porcelains; in ceramics, glazes and enamels to protect from discoloring; and as a additive to soils.

DescriptionThe blue, crystalline hydrate Co2(SO4)3.18H2O is prepared by the oxidation of cobalt(II) sulphate in 8N sulphuric acid either electrolytically or chemically with ozone or fluorine. It is stable in the dry state, but is decomposed by water with evolution of oxygen; it is fairly stable in solution in dilute sulphuric acid. Cobalt(III) alums MCo(SO4)2.12H2O (M = K, Rb, Cs or NH4) can be isolated as blue crystals from the mixed cooler solutions of the two sulphates in dilute sulphuric acid. The potassium alum is diamagnetic, the rubidium salt has a magnetic moment less than 1 B.M. and the ammonium alum has a moment of 2.1 B.M. at 304°K. The hydrated sulphate also has a small positive magnetic susceptibility. The sulphate is believed like the alums to contain the [Co(H2O)6]3+ ion.

UsesCeramics, pigments, glazes, in plating baths for cobalt, additive to soils, catalyst, paint and ink drier, storage batteries.

UsesCobalt(II) Sulphate is used in batteries and fuel cells that display long-term stability.

General DescriptionOdorless rose-pink solid. Sinks and mixes with water.

PreparationCobalt(II) sulfate is prepared by dissolving cobalt(II) oxide, hydroxide or carbonate in dilute sulfuric acid, followed by crystallization: CoO + H2SO4 → CoSO4 + H2O Co(OH)2 + H2SO4 → CoSO4 + 2H2O CoCO3 + H2SO4 → CoSO4 + CO2 + H2O Crystallization yields the commercial product, pink heptahydrate. Further oxidation of this salt in dilute H2SO4 with ozone or fluorine produces hydrated cobalt(III) sulfate, Co2(SO4)3•18H2O. This blue octadecahydrate, Co2(SO4)3•18H2O also is obtained by electrolytic oxidation of cobalt(II) chloride or any cobalt(II) salt solution in 8M sulfuric acid.