ABSORPTIVE POWER OF THE SOIL. 343 
is diminished or even destroyed by burning or calcination. 
Peters, experimenting on this point, obtained the follow- 
ing results : 
Potash absorbed from solution of chloride of potassium by 
unburned burned 
Vegetable mould, 0.2515 0.0202 
Loam, 0.1841 0.1200 - 
The Cause of the Absorptive Power of Soils for 
Bases when combined with chlorine, sulphuric, and nitric 
acids, has been the subject of several extensive investiga- 
tions. Way, in his papers already referred to, was led to 
conclude that the quality in question belongs to some pe- 
culiar compound or compounds that are associated with 
the clayey or impalpable portion of the soil. That these 
bodies were compounds of the bases of the soil with 
silica, was a most probable and legitimate hypothesis, 
which he at once sought to test by experiment. 
Various natural silicates, feldspars, and others, and some 
artificial preparations, were examined, but found to be 
destitute of action. Finally, a silicate of alumina and 
soda containing water was prepared, which possessed ab- 
sorptive properties. 
To produce this compound, pure alumina was dissolved 
in solution of caustic soda on the one hand, and pure silica 
in the same solution on the other. On mingling the two 
liquids, a white precipitate separated, which, when washed 
from soluble matters and dried at 212°, had the following 
composition * ; 
Silica, 46.1 
Alumina, 26.1 
Soda, 15.8 
Water, 12.0 
— 
100.0 
'#* Way gives the composition of the anhydrous salt, and says it contained, 
dried at 212°, about 12 per cent of water. In the above statement this water is in- 
cluded, since it is obviously an essential ingredient. 
