Feb. s, 1917 
Measurement of Inactive Moisture in Soil 
197 
After a thorough consideration it became apparent that the freezing- 
point method could not give a quantitative estimation of this inactive 
or unfree water without having to follow a rather complicated procedure. 
It could show only qualitatively that soils do cause water to become 
♦ inactive and that the amount of this inactive water varied with the 
different soils. A search therefore was instituted to find some method 
which was simple, rapid, and accurate, and which could determine quan¬ 
titatively the amount of water that the various soils cause to become 
inactive. After a considerable search the dilatometer method was chosen 
as the most promising for accomplishing the object. 
The dilatometer method is an old one. The writer used it in the 
physical-chemical laboratory of Prof, G. Tamman at Gottingen University 
in 1913. Its employment, however, in the present study received the 
impetus from the work of Foote and Saxton (5), of Yale University. 
It is an interesting coincidence that this work of Foote and Saxton, 
which really deals with the different forms of water held by the various 
hydrogels, appeared in March, ^916, while the writer's work (2), which 
contains the evidences bearing upon the ability of soils to cause water 
to become inactive, appeared in December, 1915, or only three months 
earlier. It will be of interest to mention that Foote and Saxton, using the 
dilatometer method, and the writer the freezing-point method, arrived 
independently at the conclusion that a considerable amount of water in 
certain solid substances refused to freeze, and consequently must exist 
in an inactive or combined form. 
Although the idea of employing the dilatometer method to attain the 
writer's object received its impetus from the work of Foote and Saxton, 
the procedure followed and the form of apparatus used were devised in 
the course of the investigation and are entirely original and very different. 
As a matter of fact, Foote and Saxton give no description of the apparatus 
they employed, merely saying, “The dilatometer had the usual form." 
PRINCIPLE OF THE METHOD 
The principle of the dilatometer method as employed in the present 
investigation is based upon the fact that water expands upon freezing. 
If the amount of expansion that a certain quantity of water, 1 gm., 
produces upon freezing is known, then the amount of water that freezes 
in the soil can be calculated from the magnitude of expansion produced. 
If, also, the total water content in the soil is known, the amount that does 
not freeze can be ascertained by the difference. 
DESCRIPTION OF THE METHOD AND PROCEDURE 
A large amount of time was spent in endeavoring to devise a dilatometer 
which would be simple and give accurate and concordant results. A 
large number of dilatometers of different forms were tried; but they were 
