REVERSIBILITY OF THE COLLOIDAL CONDITION OF SOILS 509 
hydrolysis. It was observed that bacterial activity, as judged by the 
appearance of gases, was especially great in the Clyde soil. That previous 
drying of a soil increases its bacterial activity has been shown by Klein 
(1915) and by others. 
TABLE 15. Apsorprion or Water Vapor sy Sorts IMMERSED IN WaTER FoR Two 
YEARS 
Per cent of 
Soil Treatment water vapor Difference 
adsorbed 
Dunkirk surface..... PNITECLT LG ieee el eee rae ee 2.77+0.02 
0.13-+0.02 
Uinderawaterst nari ean ee 2.90+0.01 
Clyde surface....... PAN TECEIG Clleheae tee Pee Pepe A ea kes 10.50+0.003 
0.40+0.005 
WinGlar Wwalieien ou ec ae socom aeabooneoc 10.10-++0.004 
———— 
Effect of leaching.— The effect of leaching on the colloidal content of 
soils is of more importance than the amount of work done on this point 
would indicate. It was studied only briefly. The data are presented in 
table 16: 
TABLE 16. Apsorprion oF WATER VAPOR BY LEACHED AND BY UNLEACHED SOIL 
~ Per cent of 
Soil treatment water vapor Difference 
adsorbed 
ciclic ener teers Orne k een PER Dose i i EM ner ik ae 4.46+0.01 
1.44+0.02 
imlestc he demer ere are. sheeted s Meee SO eT a ie 3.02+0.02 
Dye-adsorption experiments 
The dye-adsorption experiments were carried on with the same kinds 
of soils and some of the same treatments as have already been mentioned 
in connection with water-vapor-adsorption experiments. 
