Chemical elements
  Tin
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Tetramethyl Stannane
      Methyl stannic chloride
      Tin Tetra-ethyl
      Tin Tri-ethyl
      Stannous Fluoride
      Stannic Fluoride
      Sodium Stannifluoride
      Potassium Stannifluoride
      Ammonium Stannifluoride
      Stannous Chloride
      Stannic Chloride
      Chlorostannates
      Stannous Bromide
      Stannic Bromide
      Stannous Iodide
      Stannic Iodide
      Mixed Stannic Halides
      Stannous Oxide
      Stannous Hydroxide
      Stannic Oxide
      Potassium Stannate
      Stannic Acid and its Derivatives
      Parastannic Acid
      Stannyl Chloride
      Parastannyl Chloride
      Stannous Sulphide
      Stannic Sulphide
      Stannic Oxysulphide
      Stannic Iodosulphide
      Stannous Sulphate
      Stannic Sulphate
      Stannic Nitrate
      Stannous Nitrate
      Phosphor-tin
      Stannioxalic Acid
      Stannous Tartrate
      Tin and Silicon
      Stannous Tungstate
    PDB 3e94-3kwy

Stannous Sulphide, SnS






Stannous Sulphide, SnS, is formed in the dry way when tin-foil is heated with sulphur; the metal, indeed, takes fire spontaneously when brought into sulphur vapour. This sulphide may be sublimed in a current of hydrogen, and forms a shining crystalline mass, resembling graphite. Glistening, metallic scales are also formed when the sulphide is heated in the electric furnace. Stannous sulphide melts at 881° C., and boils at 1090° C., producing a green vapour; and when heated to 265° C. under pressure it decomposes into tin and stannic sulphide, thus:

2SnS = Sn + SnS2.

Stannous sulphide is precipitated in a brown, hydrated form when a slightly acidified solution of stannous chloride is saturated with hydrogen sulphide gas; on drying, the precipitate turns black. The solubility of this precipitate in acids and alkalis is instructive. Thus it readily dissolves even in somewhat diluted hydrochloric acid, and consequently is imperfectly precipitated if much acid is present, the reaction

SnCl2 + H2SSnS + 2HCl

being a reversible one which proceeds to an equilibrium.

This solubility may be referred to the base producing properties of tin; and consequently, as might be inferred, stannous sulphide is indifferently soluble in alkali solutions, though its solubility varies with its physical state. The freshly precipitated sulphide dissolves slowly on boiling with dilute caustic soda, solution, producing a mixture of stannite and thiostannite. Since the former salt is HSnOONa, the latter is probably constituted similarly, so that the reaction is:

2SnS + 2NaOH = HSnOONa + HSnSSNa.

The sulphide is reprecipitated from this solution by acid. Strong alkali may, however, decompose stannous sulphide into stannic sulphide and tin, the former of which dissolves, forming thiostannate, whilst the latter reacts with the alkali, producing stannate with evolution of hydrogen, thus:

6SnS + 6NaOH = Na2SnO3 + 2Na2SnS3 + 3H2O + 3Sn
3Sn + 6NaOH + 3H2O = 3Na2SnO3 + 6H2.


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