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THERMODYNAMIC calculations of AG for all possible transformations of metakaolin at the temperature of the first DTA exothermic peak indicates that the most stable transformation is the one that yields mullite rather than y-alumina.The energy of crystalUzation of y-alumina is quite small-36,513 cal per mol, compared with the energy of crystallization of mullite-336,180 cal per mol. Furthermore, the crystallization of y-alumina is very slow, and the crystal growth never produces crystallite sizes much larger than the lower end of the colloidal region. Hence, the gradual release of the small amounts of energy liberated during the crystallization of y-alumina would be extremely difficult to detect by DTA methods.

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Vol. 68 butyl peroxides have also been prepared having ¿-butyl alcohol of crystallization.3. The pyrolysis of ¿-butyl hydroperoxide has been studied at 95-100°and at 250°. At 95-100°¿ -butyl alcohol and oxygen are the only products formed, while at 250°the products formed are acetone, methyl alcohol, ¿-butyl alcohol, formaldehyde and water.4. The pyrolysis of di-¿-butyl peroxide has been studied at 200, 250 and 300°. Acetone and ethane are the only products formed.5. A free radical mechanism has been proposed to explain the pyrolysis of both ¿-butyl hydroperoxide and di-¿-butyl peroxide.Cambridge 39, Massachusetts

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