Accession Number : AD0010066


Title :   HEAT CAPACITY OF AMMONIUM CHROMIUM ALUM


Corporate Author : OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS CRYOGENIC LAB


Personal Author(s) : JOHNSTON, HERRICK L ; HU, JIH-HING ; HORTON, WILLIAM S


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/010066.pdf


Report Date : 20 Apr 1953


Pagination or Media Count : 21


Abstract : The heat capacity of 2 samples of NH4Cr(SO4)2 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.


Descriptors :   *SPECIFIC HEAT , PRODUCTION , LIQUIDS , CRYSTALS , ENTROPY , HYSTERESIS , SUPERCOOLING , VOLUME , COOLING


Subject Categories : Thermodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE