Chemical elements
    Physical Properties
    Chemical Properties
      Cobaltous Fluoride
      Hydrated Cobaltous Fluoride
      Cobaltic Fluoride
      Cobaltous Chloride
      Cobaltic Chloride
      Cobaltous Bromide
      Cobaltous Iodide
      Cobalt Oxy-fluoride
      Cobalt Oxy-chloride
      Cobalt Chlorate
      Cobalt Perchlorate
      Cobalt Bromate
      Cobalt Iodate
      Cobalt Monoxide
      Cobaltous Hydroxide
      Tri-cobalt Tetroxide
      Cobalt Sesquioxide
      Hydrated Cobaltic Oxide
      Cobalt Dioxide
      Cobalt Monosulphide
      Tricobalt Tetrasulphide
      Cobalt Sesquisulphide
      Cobalt Disulphide
      Cobalt Polysulphides
      Cobaltous Sulphite
      Cobaltic Sulphite
      Cobalt Thiosulphate
      Cobalt Dithionate
      Cobalt Sulphate
      Ammonium Cobalt Sulphate
      Potassium Cobalt Sulphate
      Cobaltic Sulphate
      Ammonium Cobalt Alum
      Potassium Cobalt Alum
      Cobalt Subselenide
      Cobalt Selenide
      Tricobalt Tetraselenide
      Cobalt Sesquiselenide
      Cobalt Diselenide
      Cobalt Selenite
      Cobalt Diselenite
      Cobalt Triselenite
      Cobaltous Selenate
      Cobaltic Selenate
      Cobalt Sesquitelluride
      Cobalt Tellurite
      Cobalt Chromate
      Cobalt Dichromate
      Double Chromates
      Cobalt Molybdate
      Cobalt Nitride
      Cobalt Azoimide
      Potassium Cobaltous Nitrite
      Potassium Cobalti-nitrite
      Sodium Cobalti-nitrite
      Sodium Potassium Cobalti-nitrite
      Ammonium Cobalti-nitrite
      Barium Cobalti-nitrite
      Red Sodium Cobalti-nitrite
      Red Barium Cobalti-nitrite
      Red Strontium Cobalti-nitrite
      Zinc Cobalti-tri-nitrite
      Silver Cobalti-tri-nitrite
      Cobaltous Nitrate
      Cobaltic Nitrate
      Cobalt Subphosphide
      Cobalt Sesquiphosphide
      Tri-cobalt Diphosphide
      Tetra-cobalt Triphosphide
      Cobalt Hypophosphite
      Cobalt Phosphite
      Cobalt Metaphosphate
      Tri-cobalt Di-arsenide
      Cobalt Monarsenide
      Cobalt Tri-arsenide
      Cobalt Arsenites
      Cobalt Arsenates
      Cobalt Antimonide
      Cobalt Di-antimonide
      Cobalt Antimonate
      Cobalt Thio-antimonite
      Cobalt Carbide
      Cobalt Tetra-carbonyl
      Cobaltous Carbonate
      Basic Cobaltous Carbonates
      Cobaltic Carbonate
      Cobaltous Cyanide
      Potassium Cobalto-cyanide
      Nickel Cobalto-cyanide
      Cobaltous Cobalto-cyanide
      Zinc Cobalto-cyanide
      Cobalti-cyanic Acid
      Ammonium Cobalti-cyanide
      Barium Cobalti-cyanide
      Potassium Cobalti-cyanide
      Cobalt Cobalti-cyanide
      Cupric Cobalti-cyanide
      Ferrous Cobalti-cyanide
      Nickel Cobalti-cyanide
      Silver Cobalti-cyanide
      Lead Cobalti-cyanide
      Sodium Cobalti-cyanide
      Cobalt Thiocyanate
      Cobalt Subsilicide
      Cobalt Monosilicide
      Cobalt Disilicide
      Cobalt Orthosilicate
      Cobalt Fluosilicate
    PDB 1a0c-1epy
    PDB 1et4-1k7y
    PDB 1k98-1r6x
    PDB 1r8k-1v9b
    PDB 1vl3-212d
    PDB 222d-2eff
    PDB 2ehd-2j3z
    PDB 2j4j-2r1p
    PDB 2r2s-331d
    PDB 362d-3fqw
    PDB 3ft6-3igy
    PDB 3igz-3o0n
    PDB 3o0o-4req
    PDB 4xim-9icb

Cobalt Sulphate, CoSO4

Cobalt Sulphate, CoSO4, is obtained in the anhydrous condition by raising any of its hydrates to dull redness, or by simply maintaining the heptahydrate at 250° C. until all the water has been expelled; by evaporation of a solution of any of its hydrates in concentrated sulphuric acid; or by heating a hydrate with ammonium sulphate.

By the last of these methods the salt is obtained in stable, purple- red, truncated octahedra, of density 3.65. With ammonia it yields the hexammoniate, CoSO4.6NH3. Heated in a tube open at both ends, anhydrous cobalt sulphate begins to decompose at 718° C., yielding cobalt monoxide.

Anhydrous cobalt sulphate is very stable in air at ordinary temperatures, and dissolves but slowly in hot water. The solution can be more readily prepared by dissolving the oxides or carbonate in dilute sulphuric acid. Upon evaporation at room temperatures the hepta-hydrate, CoSO4.7H2O, crystallises out. A convenient method of preparing this hydrate consists in dissolving tricobalt tetroxide in hydrochloric acid, adding an equivalent of sulphuric acid and allowing to crystallise after evaporating off the hydrogen chloride. Obtained in this manner the crystals are acidic, but may be freed from acid by precipitation from aqueous solution with alcohol and recrystallisation from pure water.

The crystals are red in colour, of density 1.924, and isomorphous with their iron and nickel analogues. They melt at 96° to 98° C., and effloresce upon exposure to air, losing one molecule of water. Practically insoluble in absolute ethyl alcohol, the crystals readily dissolve in methyl alcohol and in water, the solubility in the last-named solvent being as follows:

Temperature ° С.01020406080100
Grams CoSO4 in 100 grams H2O25.5530.5536.2148.8560.470.083.0

The heptahydrate is found in nature as the mineral cobalt vitriol or bieberite.

A concentrated solution of cobalt sulphate maintained at 25° C. deposits monoclinic crystals of the hexahydrate, CoSO4.6H2O, isomorphous with its zinc sulphate analogue. Density 2.019.

The pentahydrate, CoSO4.5H2O, was stated to result on exposing the heptahydrate over concentrated sulphuric acid. Density 2.134.

The tetrahydrate, CoSO4.4H2O, is obtained by exposing finely powdered heptahydrate to desiccation over sulphuric acid until a constant weight is arrived at. It is also produced by pouring the concentrated solution into sulphuric acid. Density 2.327.

The trihydrate, CoSO4.3H2O. The existence of this hydrate has not as yet been definitely ascertained.

The dihydrate, CoSO4.2H2O, is obtained by boiling the heptahydrate in a fine state of division in absolute alcohol. Density 2.712.

The monohydrate, CoSO4.H2O, is precipitated on adding excess of concentrated sulphuric acid to an aqueous solution of cobalt sulphate; by evaporation of an acid solution of the salt on the sand-bath until sulphur dioxide is evolved; and by heating the heptahydrate to 100° C. until no further loss in weight accrues; by decomposition of purpureo-cobalt chloride in a small quantity of water with concentrated sulphuric acid until the salt has passed into solution. The whole is then heated to 220° C. on a sand-bath. On cooling the acid is decanted, the salt washed with cold water, and finally with alcohol.

As prepared in this manner cobalt sulphate monohydrate is a red, crystalline powder, very slowly soluble in water. Exposed to moist air it slowly absorbs water. At red heat it loses water, becoming anhydrous. Density 3.125.

Basic Cobalt Sulphates

Several of these have been described as resulting on addition of ammonia, cobalt carbonate or calcium carbonate to solutions of cobalt sulphate under varying conditions. The products obtained consist of blue, bluish green, and lilac precipitates of variable composition.

Double Salts

Numerous double salts of cobalt sulphate have been prepared. Chief amongst these are salts of the type M2SO4.CoSO4.6H2O, where M stands for ammonium or an alkali metal - potassium, rubidium, or caesium. Each of these salts has been obtained and its crystallographic constants determined. The series is isomorphous with the corresponding ferrous and nickel double salts, and with their double selenates; the individual salts are discussed below. Other double salts are cupric cobaltous sulphate, CuSO4.2CoSO4.3H2O, and cobaltous nickel sulphate, (Co, Ni)SO4.H2O, in which the cobalt and nickel appear interchangeable.
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