Aug. 28. 1916 Indirect Determination of Hygroscopic Coefficient 



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Table IV shows the values for the hygroscopic coefficients calculated 

 from the moisture equivalents, using the Briggs-Shantz formula, and the 

 departure from those directly determined. In all cases the values are 

 more or less too low; using these there might appear to be as much as 

 from 1.0 to 2.8 per cent of free water in the case of a subsoil which actually 

 carried none. 



TABLE IV. — The hygroscopic coefficients calculated from the moisture equivalents and 

 the departure of these from the values obtained by direct determination 



(a) calculated hygroscopic coefficients 



(b) departure from directly determined values 



Table V gives similar data on another set of samples from the same 30 

 fields. These consisted of i-inch sections from the surface foot (2, p. 206). 

 In the case of these, however, each datum on hygroscopic coefficients as 

 well as on moisture equivalents is the mean of only duplicate determina- 

 tions. The ratio averages 2.75, compared with 2.71 found by Briggs and 

 Shantz (Table I), and varies from 2.33 to 3.29, a range of 41 per cent, 

 compared with 40 found by them with their 17 soils. Their samples also 

 were probably surface soils rather than subsoils, such as predominate 

 in Table III. In the inch sections, as in the foot sections, a decrease in 

 the ratio is to be observed in passing from the surface to the subsoil. 

 This may be attributed to the organic matter which appears to have a 

 marked influence upon the moisture equivalent, although it shows little 

 effect upon the hygroscopic coefficient (2, p. 217). Briggs and McLane 

 (5, p. 18), found that organic matter had practically the same effect upon 

 the moisture equivalent as an equal amount of clay. 



