May 5. xgas 
Movement of Soil Moisture upon Freezing 
429 
Results of the same type are also obtained on natural field soils. In 
Table II are shown the results with a silt loam taken from the field when the 
moisture content was moderately low and the soil had a crumb structure. 
Tabi<^ II .—Effect of alternate freezing^ thawing, stirring^ and standing on the freezing- 
point depression of afield soil {silt loam) 
Treatment. 
Freezing- 
point 
depression. 
First freezing. 
•c. 
1.150 
.870 
1.230 
.880 
Second freezing. 
Stirred gently in tube... 
Frozen once after stirring. 
Cooled at —10° C. for several hours. 
.680 
These results, obtained from the natural soil, agree perfectly with and 
confirm those from the artificially moistened soil. The question is, 
therefore, what factor is responsible for the great influence on the freez¬ 
ing-point depression of alternate freezing, thawing, stirring, and standing 
of the soils? 
Before the effect of stirring upon the freezing-point depression was 
discovered, it was thought that the diminution of the lowering of &e 
freezing point was due, at least partly, to the coagulation of the colloids 
upon freezing, and to the consequent liberation of unfree water from 
the colloids. The hypothesis ^ advanced was that the unfree water had a 
lower concentration than the free water, and upon its liberation it went 
to dilute the free water and thereby increased its freezing-point lowering. 
In view of the effect of stirring, however, this coagulation theory does 
not appear to afford the whole explanation for the phenomenon. 
The most logical and plausible explanation that now presents itself 
is the assumption that, upon freezing, Ae moisture in the small capillaries 
and that surrounding the particles as thick films accumulates in the larger 
capillaries of the soil by the force of crystallization. In oth^ words, fibe 
water in the larger capillaries, upon freezing, draws upon itself by the 
force of crystallization the water from the finer or smaller capillaries 
and films around the soil particles, and grows at their expense. Thus the 
water in the large capillaries affects the freezing-point depression differ¬ 
ently from that in the small capillaries. How this is accomplished will 
be discussed later. Meanwhile, further evidence is here offered indicat¬ 
ing that water moves from the small to the large capillaries upon freezing. 
When a soil with low moisture content is frozen, small droplets or 
particles of ice are formed at different places in the soil mass. These 
ice particles or droplets occur in soils both under laboratory and field 
conditions and can be seen very readily and distinctly even with the 
naked eye. Upon close examination it is found that they occur mainly 
in the most porous places or in the largest capillary spaces between the 
soil particles. 
However, when the soil is very moist and the freezing process is not 
too rapid, the moisture freezes at the surface of the soil in the form of 
^ Bo^oucxjs, George J. thb concentration of the son. solution around the son, partkxes. In 
Soil Sci., V. II, p. 131-138. 1921. 
