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Thermal Analysis at Low Temperatures

Frank E. E. Germann
1922 Physical Review  
0 C.-A thermo-junction was placed in 0.5 cc. of a^olution of known concentration and galvanometer readings were taken every 10 seconds during the cooling. At about -35 0 a rapid evolution of heat took place accompanied by expansion sufficient to break the glass tube if the solution filled more than the rounded bottom. On heating the solution a corresponding absorption of heat was observed at -20 0 . From the observed temperature changes and the specific heat the amount of heat evolved or
more » ... t evolved or absorbed was computed. The results of 67 experiments in which the concentration was varied from 10 to 55 per cent, were plotted and show a sharp maximum at 48.0 per cent, for the evolved heat and at 47.5 per cent, for the absorbed heat. New Compound Discovered by Thermal Analysis, Uranyl Nitrate Icositetrahydrate.-The above results point to the formation at -35 0 of the compound U02(N03)2.24H20, which has a less density than the hexahydrate and which decomposes spontaneously at -20 0 . This compound is of special interest in connection with the study of the relation between composition and the fluorescence and absorption of the spectra uranyl hydrates. [SECOND LSERIES . VOL. XIX.l No. 6. J THERMAL ANALYSIS AT LOW TEMPERATURES.
doi:10.1103/physrev.19.623 fatcat:3hh77uj3ljc4titm3z5yf3rmjy