Abstract
The heat capacity of urea was measured with an adiabatic calorimeter in the temperature range 15–310 K. The data were extrapolated to 0 K by a model function to derive some standard thermodynamic functions including the enthalpy increments Δ T0 H, the entropy increments Δ T0 S, and the Giauque function (=Δ TS0 −Δ T0 H/T). A simple model for the reproduction of the experimental heat capacities of urea, based on the Debye and Einstein functions, is described. The Debye characteristic temperature determined in this way was compared with those calculated from properties other than the heat capacity. Any positive evidence of a suggested phase transition in urea around 190 K was not observed in the present heat capacity measurements. Possible existence of a phase with a Gibbs energy lower than that realized in the present investigation is discussed briefly.
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References
S. Swaminathan, B. M. Craven, and R. K. McMullan, Acta Crystallogr. Sect. B 40:300 (1984).
R. A. Ruehrwein and H. M. Huffman, J. Am. Chem. Soc. 68:1759 (1946).
K. Sasaki and T. Yokotake, Tokyo Kogyo Shikensho Hokoku 61 (8):309 (1966).
M. Gambino and J. P. Bros, Thermochim. Acta 127:223 (1988).
P. Ferloni and G. Della Gatta, Abstracts of the 10th IUPAC Conference on Chemical Thermodynamics, Prague, Aug. 29–Sept. 2 (1988), p. H20.
L. Lebioda, S. Hodorowicz, and K. Lewinski, Phys. Status Solidi A 49:K27 (1978).
I. Grabowska and R. Kaliszan, Chem. Abstr. 82:77042r (1975).
T. Matsuo and H. Suga, Thermochim. Acta 88:149 (1985).
A. Yamaguchi, T. Miyazawa, T. Shimanouchi, and S. Mizushima, Spectrochim. Acta 10:170 (1957).
K. Liapis, U. A. Jayasooriya, S. F. A. Kettle, J. Eckert, J. A. Goldstone, and A. D. Taylor., J. Phys. Chem. 89:4560 (1985).
J. Lefebvre, H. Fontaine, and R. Fouretu, J. Raman Spectrosc. 4:173 (1975).
G. Fischer and J. Zarembowitch, C.R. Acad. Sci. (Paris) Ser. B 270:852 (1970).
H. Guth, G. Heger, S. Klein, W. Treutmann, and C. Scheringer, Z. Kristallogr. 153:237 (1980).
H. B. Callen, Thermodynamics (Wiley, New York, 1960), p. 354.
Fr. Lösch, Landolt-Börnstein, II/4, 1961, p. 743.
J. M. Ziman, Principles of the Theory of Solids, 2nd ed. (Cambridge University Press, Cambridge, 1972), pp. 65, 67.
N. Sklar, M. E. Senko, and B. Post, Acta Cryst. 14:716 (1961).
A. Yoshihara and E. R. Bernstein, J. Chem. Phys. 77:5319 (1982).
M. Y. Khilji, W. F. Sherman, and G. R. Wilkinson, J. Mol. Struct. 143:109 (1986).
P. W. Bridgman, Proc. Am. Acad. Arts. Sci. 52:106 (1916).
M. Y. Khilji, W. F. Sherman, and G. R. Wilkinson, Raman Spectrosc., Proc. 8th Int. Conf. (1982), p. 481.
S. D. Hamann and M. Linton, High Temp. High Press. 7:165 (1975).
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Andersson, O., Matsuo, T., Suga, H. et al. Low-temperature heat capacity of urea. Int J Thermophys 14, 149–158 (1993). https://doi.org/10.1007/BF00522668
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DOI: https://doi.org/10.1007/BF00522668