HEAT CAPACITY OF AMMONIUM CHROMIUM ALUM
OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS CRYOGENIC LAB
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The heat capacity of 2 samples of NH4CrSO42 12H2O was measured from 18 to 305 K. A second-order transition was found in the region between 92 and 97 K with a heat and entropy of transition equal to 267.4 or - 0.1 cal and 2.83 or - 0.1 EU, respectively. The transition tended to disappear under supercooling conditions. The results are compared with the observations of Kraus and Nutting J. Chem. Phys. 9 133, 1941. The samples which showed transitions became opaque after a few minutes in the N or H cooling liquid, as though they were broken into an infinite number of tiny crystals by the disruption of the lattice. The production of the multicrystalline material was attributed to a volume change under hysteresis conditions.