Chemical elements
    Physical Properties
    Chemical Properties
      Indium Trifluoride
      Indium monochloride
      Indium dichloride
      Indium trichloride
      Indium oxychloride
      Indium monobromide
      Indium tribromide
      Indium oxybromide
      Indium mono-iodide
      Indium di-iodide
      Indium tri-iodide
      Indium perchlorate
      Indium iodate
      Indium sesqui-oxide
      Indium hydroxide
      Indium monosulphide
      Indium disulphide
      Indium sesquisulphide
      Indium trisulphide
      Basic indium sulphite
      Indium sulphate
      Indium sesquiselenide
      Indium selenite
      Indium selenate
      Indium telluride
      Indium silicotungstates
      Indium nitrate
      Indium phosphide
      Indium platinocyanide
      Indium oxalate
      Indium acetylacetonate
    PDB 1ind-1ind

Indium sulphate, In2(SO4)3

Indium sulphate, In2(SO4)3, may be prepared by dissolving indium, indium sesqui-oxide, or indium hydroxide in sulphuric acid, and carefully heating to expel water and excess of sulphuric acid. It is a white solid, very hygroscopic and extremely soluble in water, from which it is exceedingly difficult to crystallise out a hydrated sulphate. An ennea-hydrate, In2(SO4)3.9H2O, is said to exist, and an acid salt of the composition In2(SO4)3.H2SO4.8H2O is described as separating from an acid solution of the sulphate when evaporated over concentrated sulphuric acid.

The anhydrous sulphate has a density of 3.44 and a specific heat (between 0° and 100°) of 0.129.

Various double sulphates have been prepared by mixing indium sulphate solutions with solutions of other sulphates. The ammonium-, rubidium-, and caesium-indium alums, M2SO4.In2(SO4)3.24H2O (M = NH4, Rb, or Cs), can be thus prepared, the first having been discovered by Roessler and the others by Soret. Lithium, sodium, and potassium alums are not known, but sodium indium sulphate, Na2SO4.In2(SO4)3.8H2O, and the corresponding potassium, ammonium, and thallium salts have been prepared.

The three alums separate out in regular octahedra or combinations of the octahedron and cube. Their aqueous solutions have an acid reaction, and when heated become turbid owing to the separation of basic sulphates or, in the case of the caesium salt, indium hydroxide. The melting-points and solubilities of the alums in water (in grams of crystalline salt per 100 grams of water) are as follows : -

Temperature, °C.15°16.5°25°30°
Ammonium indium alumm.p. 36°...c. 200...c. 400
Rubidium indium alumm.p. 42°44.28.........
Caesium indium alumm.p. ?...3.04c. 11.7...

In the case of the ammonium alum, the "melting-point" is known to denote the transition-point, above which the alum breaks up into the octahydrate and water (Roessler): -

(NH4)2SO4.In2(SO4)3.24H2O ⇔ (NH4)2SO4.In2(SO4)3.8H2O + 16H2O.

The densities and refractive indices of the alums for the D-line at the ordinary temperature are given by Soret as follows: -


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