PRACTICE XXIII 



DETERMINATION OF THE RATE OF PERCOLATION OF AIR 



THROUGH SOILS 



This Practice may be done as a class exercise, the instructor 

 arranging the apparatus, and the student making frequent 

 observations. 



This experiment requires the utmost care in order to obtain 

 satisfactory results. Use '' pressure " or '' double-thickness " 

 tubing. 



Fill the tubes very carefully without compacting, holding 

 them vertically while filling. Use sand, brown silt loam, gray 

 silt or gray silt loam, clay or clay loam, and peat. Connect the 

 soil tube with the top of the aspirator bottle. Re sure that all 

 connections are air-tight. Open the cock, allowing the force of 

 gravity to draw the water out of bottle by pulling air in through 

 the soil in the tubes. Note and record the time required to collect 

 1 liter of water. Repeat with the soil compacted* as in Practice 

 XL Repeat both loose and compact with sand and 10 per cent 

 peat, gray silt or gray silt loam with 10 per cent peat, brown silt 

 loam and 10 per cent peat, loess, and loess and 10 per cent peat. 



It may be tried by wetting the soil. 



What bearing has this practice upon aeration ? 



What effect Jias oro-anic matter on aeration ? 



What effect will moisture have on aeration ? 



References. 



"Soils," Lyon and Fippin, })p. -116-^17 and 4:)7-44:t). 

 "The Soil," King-, pp. 2:59-252. 

 'Soils," Ililgard, pp. 279-280. 



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