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 Iodide, SnI2






Stannous Iodide, SnI2, is obtained by adding potassium iodide in slight excess to a concentrated solution of stannous chloride, or by the action of hydriodic acid on tin; it crystallises in orange-red octahedra, which may be obtained by melting the compound, or evaporating its solution in carbon disulphide; but it is probably dimorphous. It melts at 320° C., and boils at 720° C. The dihydrate SnI2.2H2O is said to exist; 100 parts of water dissolve 0.93 parts of anhydrous stannous iodide at 20° C., and 4.03 parts at 100° C. It is much more soluble in hydriodic acid and alkali halide solutions, owing to the formation of a complex acid or salts.

When a solution of stannous chloride is titrated with iodine it is sometimes assumed that an additive reaction takes place with the formation of stannic iodochloride, SnCl2I2; but most likely a mixture of stannic chloride and iodide is produced thus:

2SnCl2 + 2I2 = SnCl4 + SnI4;

stannic iodide is, however, reduced to stannous iodide by excess of stannous chloride, thus:

SnI4 + 2SnCl2 = 2SnI2 + SnCl4.

Stannous iodide combines with hydrogen iodide to form iodostannous acid, HSnI3; and unstable, pale yellow needles of this substance separate at 0° C. from a saturated solution of stannous iodide in hydriodic acid. To this acid there correspond the iodostannites or stannoiodides: NaSnI3.3H2O, KSnI3.3H2O, NH4SnI3.3H2O, Sr(SnI3)2, and Ba(SnI3)2, which separate when the corresponding saline iodides are added to concentrated stannous chloride solution.

Stannous iodide combines with ammonia to form the compound SnI2.2NH3, which is yellow.
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