Published: 1963
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High-temperature heat-content vaiues of pure Lu sesquioxide and Dy-sesquioxide were measured over the temperature range from 298 to 1800 deg K. Similar data for Ce sesquioxide were calculated from measurements of a mixture of Ce sesquioxide and dioxide and known values for Ce dioxide. The results for Lu sesquioxide are regular. Dysprosium sesquioxide has a minor thermal anomaly near 1590 deg K, the extra heat absorption being 220 cal/mole. Hexagonal Ce sesquioxide undergoes a transformation around 1050 deg K, which is only slowly reversible; consequently results were obtained for both the low- and high-temperature varieties. The original heat-content data are reported, and smooth values of heat content and the corresponding entropy increments are tabulated. Equations were derived to represent the heat-content values. (auth).