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The heat capacity of colorless synthetic sapphire (a Al20 a , corundum) has been measured from. 2 to 25.K. The data above 14 K can be expressed as C.= 1.755X1Q-'TB+1.905X1Q-'l]'6 ~J/K.g-atom. This equatlOn for C. gives 8 0 = 1035 K, in good agreement with the values calculated from elastic constant data. An extrapolation of these results to higher temperatures is consistent with other data. Below 14 K an anom~lous heatcapacity contribution appears which is about 1.5% of C. at its maximum. ~~e magnitu.de of ~~lS anomaly corresponds to that which would be given by a few ppm of gaseous or transltion-metallmpunties.