REVERSIBILITY OF THE COLLOIDAL CONDITION OF SOILS 505 
in the preceding experiment were kept in air-tight bottles for three months 
and were then subjected to determinations of hygroscopicity. The 
results are given in table 12: 
TABLE 12. Apvsorprion or WatER Vapor By ContinuousLy Moist AND BY REMOIS- 
TENED Sorts, THREE Montus Arter REMOISTENING 
Per cent 
Soil Treatment of water Difference 
adsorbed 
Dirnisinkesuraceseree cscs. sas: Continuously moist... .. 4.29+0.02 | 5 
Remoistened........... B20, 0 |, Dees 
Blydersunlaces.2. an... ses Continuously moist... .. 18.800.01\} 95 19.9 01 
Remoisteneds: (ohana. o: TOR/O20F OLS (Re Cetera 
These data show that after three months the hygroscopicity of the 
remoistened soils did not return to a value equal to that of the continu- 
ously moist soils, indicating that with these soils the effect of drying on 
this property is not reversible within three months at least. 
Effect of alternate wetting and drying.—The next experiment was in regard 
to the effect of alternate wetting and drying. The data are given in table 18: 
TABLE 13. Errect or ALTERNATE WETTING AND DryING oF SOILS UPON THEIR 
ADSORPTION OF WATER VAPOR 
Per cent of 
Soil Treatment water vapor Difference 
adsorbed 
Continuously;moistys. 9.42 6 eee 3.97+0.07 
0.99+0.08 
ANe-Chaeeh” Il inten, bo06 bmn bones ones 2.98+0.04 
0.05+0.06 
Dirt rape ieee si nck ts Ney we 2.93+0.04 
0.07+0.04 
2 Vi Sutin et eS ar ein EE nae tags MeN 2.86+0.02 
Dunkirk surface 0.08-+-0.09 
Shiba aey vee es a MN 2.78+0.09 
0.0640. 10 
TG aioe hee pone a ee 2.84+0.05 
0.10++0.06 
BOS Tn IPE pes aK iue, Bi Sea te er Pe 2.94+0.04 
Difference between 1 drying and 32 
TYAN S-Series ee ee a pee eal Rene cp en Lees chee asks 0.04+0.06 
