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The volume expansion of cristobalite, as it passes through the low-temperature inversion range, was studied by 'means of a dilatometer in which the cristobalite expanded against a column of mercury. The volume change was measured in a capillary tube attached to the mercury column. The temperature of inversion is a function of the previous history of the cristobalitesample. A volume change of 7% was obtained upon inversion. The volume change was found to depend on the previous heat-treatment of the sample, the presence of added catalysts, and the source and grain size of silica. All of these factors affect the amount of cristobalite present and hence the change of volume on inversion of the cristobalite. Several samples of cristobalite from used silica brick were studied. The information is applied to the problems of silica refractories.

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