PRACTICE VI 



DETERMINATION OF THE VARIATION IN THE HYGROSCOPIC 



MOISTURE OF SOILS 



In this exercise each student will use air-dry soils provided 

 for the regular class work. These are sand or sandy loam, gray 

 silt or gray silt loam, brown silt loam, clay or clay loam, and peat. 



Determine the weight of moisture lost when heated for eight 

 hours in an oven at 100 to 105*^ C. This loss is the hygroscopic 

 moisture. Express in per cent based on the weight of water- 

 free soil. All samples^ especially duplicates, should be weighed 

 out at the same time to avoid any change in the amount of mois- 

 ture due to a change in relative humidity or temperature. 



For directions in detail see Practice II. 



Explain differences between clay or clay loam and sand or 

 sandy loam ; between peat and sand or sandy loam. 



References. 



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



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



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



" The Soil," King, p. 252. 



" Soils," Hilgard, pp. 196-200. 



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