PRACTICE II 



DETERMINATION OF HYGROSCOPIC MOISTURE IN SOILS 



Use air-dry soils from Practice I after grinding thoroughly 

 in a mortar. 



Weigh the necessary weighing bottles or crucibles which have 

 been made water-free by drying in an oven at 100 C. for five 

 hours. Crucibles may be made water-free in a blast flame. Cool 

 in a desiccator before weighing. It is best to weigh out all of 

 the duplicate samples at the same time, so as to have them 

 under the same moisture conditions. The hygroscopic moisture 

 of soil varies with the temperature and relative humidity of 

 the atmosphere. 



Dry in an oven at 100 to 105 C. for at least eight hours. 

 Cool in a desiccator. Weigh rapidly to avoid the absorption of 

 much moisture from the air. The loss in weight is the hygro- 

 scopic moisture. Express in tabular form on the opposite page 

 the hygroscopic water in grams and in per cent of water-free 

 soil; also the total moisture in the samples in per cent of 



water-free soil. 







REFERENCES. 



" Soils," Lyon and Fippin, pp. 141-144. 



"The Soil," Hall, A. D., pp. 84-88. 



" Physical Properties of Soil," Warington, Robt., pp. 57-60. 



"The Soil," King, F. H., p. 252. 



