Chemical elements
    Physical properties
    Chemical properties
      Aluminium subfluoride
      Aluminium trifluoride
      Aluminium trichloride
      Aluminium tribromide
      Aluminium iodide
      Aluminium chlorate
      Aluminium perchlorate
      Aluminium bromate
      Aluminium periodate
      Aluminium suboxide
      Aluminium sesqui-oxide
      Aluminium peroxide
      Aluminium hydroxides
      Tricalcium aluminate
      Sodilim aluminate
      Aluminium sesqui-sulphide
      Aluminium selenide
      Aluminium telluride
      Aluminium sulphite
      Aluminium sulphate
      Sodium alum
      Potassium alum
      Ammonium alum
      Hydroxylamine alum
      Silver alum
      Aluminium dithionate
      Aluminium selenite
      Aluminium selenate
      Aluminium chromate
      Aluminium molybdate
      Aluminium silicomolybdate
      Aluminium tungstate
      Aluminium silicotungstate
      Aluminium phosphotungstate
      Aluminium nitride
      Aluminium phosphide
      Aluminium arsenide
      Aluminium nitrate
      Aluminium Phosphates
      Basic aluminium arsenite
      Aluminium carbide
      Aluminium carbonate
      Aluminium thiocyanate
      Aluminium oxalate
      Aluminium alkyls
      Aluminium Hydrocarbon
      Aluminium acetylacetonate
      Aluminium silicide
      Aluminium silicates
      Aluminosilicic acids aluminosilicates
      Aluminium Borides
      Aluminium Boride
      Aluminium Boride
      Aluminium borocarbides
      Aluminium borate
      Aluminium sodium perborate
    PDB 1a6e-1zca
    PDB 2b8w-3i62
    PDB 3kql-5ukd

Aluminosilicic acids, aluminosilicates

It is usual to regard the numerous known silicates, including those described in the preceding section, as the salts of various hypothetical silicic acids, or as isomorphous mixtures of such salts. There are, however, good reasons for supposing that many of the compounds usually classed as aluminium silicates are no more related to the silicates than the ferrocyanides, for instance, are related to the cyanides. Numerous reasons can be adduced in favour of the view that the alumina in numerous silicates plays the rdle of an acid and not a base, and that, as was originally proposed by Vernadski, the silicates themselves are the salts of a number of complex aluminosilicic acids, comparable with the phosphomolybdic, silicomolybdic, and silicotungstic acids, etc. For the nature of the evidence, however, the reader must be referred to the literature.

Many silicates are decomposed by the prolonged action of water and carbon dioxide, furnishing colloidal silicic acid or opal. In a similar manner, the aluminosilicates give rise to colloidal aluminosilicic acids or clays. The empirical formulae of these acids may be tabulated as follows: -

Alumino-monosilicic acid (allophanic type)Al2O3.SiO2.nH2O
Alumino-disilicic acid (kaolinic type)Al2O3.2SiO2.nH2O
Alumino-trisilicic acid (natrolitic type)Al2O3.3SiO2.nH2O
Alumino-tetrasilicic acid (pyrophyllitic type)Al2O3.4SiO2.nH2O
Alumino-pentasilicic acid (chabazitic type)Al2O3.5SiO2.nH2O
Alumino-hexasilicic acid (felspathic type)Al2O3.6SiO2.nH2O

The constitution of these acids at present can only be eonjectured. The following groupings of important compounds are due to Mellor and Holdcroft:

Alumino-monosilicates - Allophanic Type

Allophane is Al2O3.SiO2.5H2O. Salts of this type are: augite, MgO.Al2O3.SiO2; chlorite, 2MgO.Al2O3.SiO2.2H2O.

Alumino-disilicates - Kaolinic Type

Various alumino disilicic acids are: -

Among the aluminosilicates that may be looked upon as salts of the preceding acids are nephelite, K2O.Al2O3.2SiO2, and anorthite, CaO.Al2O3.2SiO2.

Alumino-trisilicates - Natrolitic Type

Salts are represented by natrolite, Na2O.Al2O3.3SiO2; garnet, 3CaO.Al2O3. 3SiO2; scolecite, CaO.Al2O3.3SiO2.3H2O; lepidolite, KLiO.Al2O3.3SiO2; etc.

Alumino-tetrasilicates - Pyrophyllitic Type

Pyrophyllite is Al2O3.4SiO2.H2O. Salts are leucite, K2O.Al2O3.4SiO2; analcite, Na2O.Al2O3.4SiO2.2H2O; spodumene, Li2O.Al2O3.4SiO2; glaucophane, Na2O.Al2O3.4SiO2; etc.

Alumino-pentasilicates - Chabazitic Type

The group is represented by chabazite, CaO.Al2O3.5SiO2.7H2O, and harmotine, BaO.Al2O8.5SiO2.6H2O.

Alumino-hexasilicates - Felspathic Type

This type is represented by orthoclase, K2O.Al2O8.6SiO2.

For further information concerning attempts to derive the constitutions of the aluminium silicates, the reader is referred to the literature.
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