410 Soil, Soil Solution and Freezing-Point Determinations 



elusion that the soil colloids are mainly operative in causing the division, 

 especially when it is noted the general equation (5) connecting free and 

 total moisture is of the familiar adsorption type. The deduction can also 

 be made that as the total moisture content varies, the relative amounts 

 of "free" and "unfree" water also change. 



We can obtain a clearer view of the conditions imposed on the soil 

 solution by this equation, if the unfree water (Z„) is considered. 



We have 



j/„=r„^z„ .... (11) 



and Y„ = cM^' (5) 



Equation (o) can be written 



4.rJ=y„ + z„, .... (12) 



:. 2„ = A i'n' = y„. • • • (13) 



This equation connects the value of the free and unfree water at 

 any moisture content, but owing to the presence of the unknown quan- 

 tity, Y21 (or ^34) '" the term -^ , the values of Z„ wiU also contain this 



same unknown. But we can proceed to obtain a series of values for Z„ 

 in a difEerent manner, using Fig. 3. If we give Y^^ any arbitrary value, 

 with the obvious restriction that it must lie between and 21, we get a 

 set of values for y„ at various known total moisture contents, and hence 

 obtain by subtraction the corresponding values of Z„. .Table V shows 

 the values for Y„ and Z„ for the sandy loam soil obtained in this manner, 

 for various assumed values of Yji between and 21. 



