Feb. 5,1917 
Measurement of Inactive Moisture in Soil 
213 
generated is due to physical phenomena only, then the amount of heat 
produced must have been the same in the benzene and toluene as that 
in the water. They also found that soils would extract the water from 
alcohol. From all these data they concluded, although not positively, 
that water must be chemically combined in soils. 
(6) In the present investigation it was found that if those soils which 
cause a large amount of water to become unfree, as indicated by the 
quantity that fails to freeze, are heated to red heat, they cause then very 
little if any water to become unfree. Indeed, they act almost like quartz 
sand. Their power to render water inactive, therefore, is destroyed by 
the process of heating. 
These results could be interpreted to mean that these soils contain 
colloids, that it is these colloids which render the water inactive by com¬ 
bining with it physically and chemically to form colloidal hydrates, and 
that these colloids are destroyed by heating and are converted into an 
irreversible condition so that they can not take up the water to combine 
with it physically and chemically and assume the hydrated state again. 
All the foregoing evidences therefore appear to indicate quite strongly 
that some of the unfree water exists in the soils as physically adsorbed 
and chemically combined. 
In view of the presence of the colloidal hydrates in the soils and in 
view of the tremendous amounts of water that many of these colloidal 
hydrates take up, it also appears that the greater portion of the unfree 
water in the soils and especially in the colloidal types is chemically 
combined rather than physically adsorbed, provided the water in the 
colloidal hydrates of alumina, silica, and iron exists as loosely chemically 
combined water and not as adsorbed water. 
The question now is, if this chemically combined and physically ad¬ 
sorbed water exists in the solid phase or as solid solution, can it be 
utilized by plants? The answer to this question may be obtained from 
the following facts: (1) This chemically combined and physically ad¬ 
sorbed water, although probably in the solid phase, is not in an absolutely 
unchangeable and unutilizable condition; it will evaporate almost like 
ordinary liquid water; it will become free by certain treatments; and 
it will be adsorbed by solid substances which exert an attraction for it, 
etc. (2) It has been found that plants will obtain water from ice (7), 
which is a solid solution. (3) In conducting soil-moisture studies Alway 
(1) and other investigators have found that plants under certain condi¬ 
tions can reduce the moisture content in the soil near the hygroscopic 
moisture content, and consequently below the wilting coefficient. 
From these considerations, therefore, it appears that plants can and 
do utilize this unfree water which is conceived to exist as physically 
adsorbed and loosely chemically combined, probably in the solid phase. 
On the other hand, the water in this condition must be held in the 
soil with a considerable force and the plants can obtain it only at an 
