46 



XXIV. B, A. Keen. " A quantitative Relation between Soil 

 and the Soil Solution brought out by Freezing- 

 point Determinations." Journal of Agricultural 

 Science, 1919. Vol. IX. pp. 400-415. 

 An analysis is made of the experimental data accumulated by 

 Bouyoucos and others in their investig-ations of the freezing-point 

 depression of the soil solution in situ under various conditions. 

 Bouyoucos finds that the soil solution in quartz sand and extreme 

 types of sandy soil behax es approximately like dilute solutions, the 

 freezing-point depression varying as the concentration, or, in the 

 present case, inversely as the moisture content, i.e., 



M„Dn = K 

 where K = constant, 0^ = freezing-point depression at moisture 

 content of ls\^. In the vast majority of soils, however, the freez- 

 ing-point depression increases much more rapidly with decreasing 

 moisture content than this equation would imply, and Bouyoucos 

 was led to suppose that the soil rendered a definite amount of water 

 " unfree," in the sense that it did not take part in the freezing- 

 point depression. 



This hypothesis is quantitatively examined in the present 

 paper, and it is shown from Bouyoucos' experimental data that : — 



1. — The water rendered unfree is not a constant amount, but 

 varies with the moisture content. 



2. — A definite relation exists between the free, unfree and 

 total moisture, expressed by the equations : — 



Yn cm;; 



/ =r. L Y^ _ y 



^■' n I I n i n 



C^ 



where c and x are constants for any one soil, 

 Mn "^ total moisture content, 

 Yn = f^ee water, 

 Zn = unfree water. 



XX\'. B. A. Keen. " The Relations existing between tJie 

 Soil and its l]\ite}' Content." Journal of Agricul- 

 tural Science, 1920. Vol. X. pp. 44-71. 



This paper is a general sur\ey of the literature of the subject. 

 Until re(X'ntly, most of the experimental data was interpreted on 

 the assumption that the moisture was distributed in a thin film 

 over the surface of the soil grains. The water in this film was 

 divided into three classes : hygroscopic, capillary and gravita- 

 tional. The gravitational water could drain away into the sub- 

 soil, the capillaty water was retained by the soil, and was capable 

 of movement therein, and the hygroscopic moisture was assumed 

 to be inc^apable of movement under (\'ipillary or gravitation.d 

 forces. 



It was found that these dixisions were insulfi(Ment to explain 

 the observed facts, and a number of auxiliary divisions and equili- 

 brium points were introduced, mainly by American workers. This 

 carried with it the serious defect that each sub-section was 

 more or less detached from its neighbours, and thus the hypothesis 



