Feb. 5,1917 
Measurement of Inactive Moisture in Soil 
205 
SIGNIFICANCE OF THE AGREEMENT OF THE VARIOUS METHODS IN INDI¬ 
CATING THE SAME PERCENTAGE OF WATER AS THAT WHICH FAILS TO 
FREEZE 
The agreement of the various methods of entirely different principle 
in giving practically the same percentage of moisture as that which fails 
to freeze under the empirical conditions already mentioned is of great 
significance. This remarkable agreement indicates that there is a crit¬ 
ical point on the moisture curve or scale at which the condition of the 
soil moisture begins to change, and this change or transformation must 
be very marked. At this point the soil water appears to change from 
the free state to an inactive or unfree condition. Whether or not the 
point of transition is abrupt can not be said definitely, but many evi¬ 
dences indicate that it is quite sudden. 
On the other hand, it must be stated that these various methods prob¬ 
ably do not indicate the absolute initial point of commencement of the 
unfree water. It is almost certain that the degree of unfree water as shown 
by the various methods is somewhat below that of the total. This is due 
to the fact that the unfree water does not exist in an absolute unchange¬ 
able and unutilizable condition, but in a state in which it can be changed 
into free water by various factors. As a consequence, the methods are 
not absolute, but are empirical—that is to say, since this unfree water 
can be converted into free water by various factors, then the amount of 
unfree water that any methods indicate will depend to a considerable 
extent upon the empirical conditions employed in that method. Thus, 
for instance, as will be shown subsequently, the amount of water that 
fails to freeze decreases with the increase in supercooling; the amount 
of unfree water therefore diminishes with greater undercooling. Again, 
the wilting coefficient of soils is not absolutely definite, but varies to a 
considerable extent with the environmental conditions which affect the 
intensity or velocity of atmospheric evaporation. 
The agreement of the foregoing methods, therefore, in indicating the 
same percentage of unfree water must be considered more as a remark¬ 
able coincidence rather than as indicating the absolute initial point of 
commencement of the unfree water and consequently the absolute total 
amount of this unfree water. 
EFFECT OF SUCCESSIVE FREEZINGS UPON THE AMOUNT OF WATER THAT 
FAILS TO FREEZE IN SOILS 
The work with the freezing-point method showed, as already men¬ 
tioned, that the lowering of the freezing point of colloidal soils at low 
moisture content decreased with successive freezings up to a certain 
number of freezings and then it became constant. This diminution was 
interpreted to mean that the soils had caused some of the water to 
