Studies in Synthetic Systems

Estdoule (1965, 1969) demonstrated that there is a discontinuity between dioctahedral and trioctahedral expanding phases in the MgO - Al O  

Velde (1963) synthesized several types of montmorillonites in the Si-Al-Mg-H O system at 2Kb pressure near 300°C. The trioctahedral forms have a substitutional series as follows  

Adjacent, but separated from this composition commences the 17 X series which continues to a very nearly non-aluminous end-member. It is assumed that the series is incomplete in this direction (i.e., at the stevensite composition which is more silica rich, (Mg2 g Si ) (Mg is QCOH. nHjO This is deduced from experiments in the system MgO-SiO2 H20 which do not produce a montmorillonite at high pressure above 250°C (Johannes, 1969  

Increasing temperature and pressure increase the compositional 

If we consider the substitutions in the trioctahedral montmorillonite structure which give rise to a charge imbalance on the basic 2 1 structure, they can be considered as being two in kind  

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