2 l6 
Journal of Agricultural Research 
Vol. VIII, No. 6 
the latter with ligroin. The bulb with its contents is then placed in a 
cooling mixture and allowed to supercool. After the desired super¬ 
cooling is attained the bulb is moved gently in the cooling mixture until 
solidification commences, which is indicated by the rise of the ligroin in 
the stem. The bulb is allowed to remain in the ice mixture with fre¬ 
quent movement until equilibrium is reached. The total rise of the 
ligroin in the stem is taken to represent the total quantity of water that 
freezes in the soil. 
It was found that not all of the water added to soils freezes, some of 
it fails to freeze, and the quantity that fails to freeze is different in the 
various classes of soil. Under the empirical conditions of 25 gm. of 
air-dry soil mixed with 5 c. c. of water, supercooled to 3 0 C. in a tem¬ 
perature of — 4 0 , the quantity that fails to freeze varies from 2 per cent 
in quartz sand to 80 per cent in clay, of the 5 c. c. of water added. It 
increases, therefore, from the simple and noncolloidal types to the 
complex and colloidal types of soil. 
In the case of colloidal soils the amount of water that fails to freeze 
decreases with the increase in supercooling, but in the case of non¬ 
colloidal soils it remains the same. 
By increasing the degree of moisture content the amount of water 
that fails to freeze is decreased in the colloidal soils, but remains prac¬ 
tically the same in the noncolloidal soils. 
At the low-moisture content successive freezings diminish the quantity 
of the unfrozen water in the case of the colloidal soils, but not in the 
noncolloidal soils. 
The percentage of water content that fails to freeze in all soils under 
the empirical conditions of 25 gm. of air-dry soil mixed with 5 c. c. of 
water, supercooled to 3 0 in a temperature of — 4 0 corresponds remark¬ 
ably closely to the moisture content known as the wilting coefficient, to 
the percentage of moisture at which solidification can not be started, to 
the thermal critical moisture content, etc. 
This water which fails to freeze is designated as unfree or inactive water. 
Its exact condition in the soil is not definitely known. There are many 
evidences, however, which indicate that a large portion of it may exist 
as physically adsorbed and loosely chemically combined, probably in 
the solid phase, or as solid solution. The quantity of the chemically 
combined probably exceeds that of the physically adsorbed. 
This physically adsorbed and chemically combined water, although 
probably in the solid phase, is not in an absolute unchangeable condi¬ 
tion, but it can be converted into free or available water, by various 
factors or treatments. Its magnitude, therefore, is not absolutely 
fixed, but varies with the empirical conditions of the method employed 
for its determination. 
