It is evident from thermodinamics that at phase transition temperature soil water and ice are balanced, and heat of crystallization is equal to the enthalpy difference of soil water and ice at a given temperature. In spite of this fact even in calorimetric measurements let alone a mathematical modeling there has been used a constant as a crystallization heat of soil water equal to crystallization heat of volume water at atmospheric pressure. Kirhgoff's equation for the enthalpy difference of volume water and ice is of frequent use in description of crystallization heat of soil water. It may be attributed to the lack af data on enthalpy of soil water. A new method has been devised to find experimentally crystallization heat of soil water. This method was used for determination of crystallization heat water in clays.

The results obtained show that crystallization heat of soil water at low moisture is much different from that of volume water. The calorimetric tests in determining unfrozen water show that an effect of the difference is much evident. For example in clay samples examined the amount of unfrozen water is 20 - 30% less at -10 C using the values of crystallization heat of soil water, compared with the ones for volume water.

Anatoly M. Timofeev
Inst. of Physical and Engineering of the North
Oktyabrskaya street, 1
677891, Russia, Yakutsk,
Phone number:  3 - 52 - 11
E-mail:fteh@yacc.yakutia.su