REVERSIBILITY OF THE COLLOIDAL ConDITION OF SoILs 513 
The differences between successive drying treatments are significant in 
every case except between air-drying and oven-drying, but the changes 
due to successive air-drying are not always in the same direction. The 
cumulative difference due to thirty-two dryings as compared with one 
drying is significant. The results are not wholly in accord with those of 
other soils similarly treated. 
In table 19 are given the effects of long immersion of soils on their 
adsorptive capacity for methylene blue: 
TABLE 19. Avsorption or METHYLENE BLUE By Sorts IMMERSED IN WATER FOR Two 
YEARS 
Corrected (C-C,) - dye 
Soil Treatment colorimetric | adsorbed per | Difference 
reading gram_.of soil 
Dunkirk surface...| Air-dried.............. 25.0+0.1 60.00.16 
14.4+0.21 
Winderwwater- as aes: 39.1+0.2 74.4+0.13 
Wivydersurtace.....| Air-dried........:..... 51.9+0.6 80.7+0.22 
8.60.22 
lWnderswaiterancy sane 93.5+0.4 89.30.04 ‘ 
The long soaking under water has increased the adsorptive capacities 
of these soils. The results with the Dunkirk soil agree with those obtained 
by water-vapor adsorption, while those with the Clyde soil do not. 
Adsorption of methylene blue by leached and by unleached soil is 
shown by table 20: 
TABLE 20. Apsorption or Mrtuytens Buur By LEACHED AND BY UNLEACHED SoIL 
Corrected (C-C,) - dye 
Soil treatment colorimetric adsorbed per | Difference 
reading gram of soil 
Weache lepers ee in titinis als ip mene eet 189.0+3.0 94.70.84 
8.2+0.84 
UTR S eG Tee he PS RUA ee i aR 74.1+40.3 86.50.06 
