CONCLUSION - SR99

20

0

20

Liquid Solution Specific Volume (m3 Mg1)

Figure 14. Relationships between unfrozen-solution specific volumes and

ice-solution capillary pressures for sand pastes warmed from 66.6C to

0C. The equilibrating solutions of the pastes were initially 0.1, 0.01, and

0.001 mol kg1 NaCl.

CONCLUSION

The minerals analyzed in this study may be thought to represent the range of ap-

plicability of capillary theory to explain the freezing behavior of porous solids. The

kaolinite samples were not composed of an expanding-lattice clay with intermedi-

ate particle size, and the experimental results from this material supported the theory

well. Sand and montmorillonite did not support it as well: sand because its particle

size (and, therefore, pore radii) was too large, and montmorillonite because it has a

much smaller particle size and because relatively large volumes of water can be

held in its interlamellar spaces for which capillary forces are less important. Our

study did indicate that capillarity theory coupled with the Pitzer model describes

acceptably the effect of an electrolyte on the freezing curves of minerals of interme-

diate size between sand and montmorillonite.

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Archer, D.G. (1992) Thermodynamic properties of the NaCl + H2O system; 2: Ther-

modynamic properties of NaCl(aq), NaCl2H2O(cr), and phase equilibria. Journal

of Physical and Chemical Reference Data, 21: 793829.

Atkins, P.W. (1990) Physical Chemistry. 4th edition. New York: W.H. Freeman and

Co.

Bader, H. (1964) Density of ice as a function of temperature and stress. USA Cold

Regions Research and Engineering Laboratory, Special Report 64.

Brun, M., A. Lallemand, J.-F. Quinson and C. Eyraud (1977) A new method for the

simultaneous determination of the size and shape of pores, The thermoporometry.

Thermochimica Acta, 21: 5988.

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