Absorption of Potash by Soils of knoicn Composition. 343 
The experiment was conducted in precisely the same manner 
as in No. 3. 
2 imperial pints of the solution, after contact with the sandy 
soil, on evaporation, gave a residue, which dried at 30(V Fahr., 
weighed 37,700 grains. This residue, on analysis, yielded the 
following results : — 
Organic matter and salts of ammonia 2-540 
Soluble silica 0-40 
Oxides of iron and alumina, with traces of phos-i .q^q 
phoric acid .. ..J 
Sulphate of lime 1'550 
Sulphate of magnesia -f>04 
Chloride of potassium - 932 
Sulphate of potash 31-847 
37-453 
The sum total of the separate constituents of this residue, it 
will be seen, agrees as well as can be expected with the amount 
obtained by direct evaporation of 2 pints of liquid. 
Calculated for 8 decigallons of liquid brought in contact w r ith 
one pound of soil, we obtain the following results : — 
Grains. 
Organic matter and salts of ammonia 8*128 
Soluble silica -128 
Oxides of iron and alumina, with traces of phos-"i .^ 0 g 
phoric acid J 
Sulphate of lime 4-960 
Sulphate of magnesia l-fil2 
Chloride of potassium 2-982 
Sulphate of potash 101-910 
119-848 
Before contact with soil, the whole solution contained 120'8 
grains of solid matter ; after contact, 119*848 grains, or very 
nearly the same amount. Whilst, however, the concentration 
of the filtered liquid was scarcely altered, its composition under- 
went material changes in its passage through the soil. 
Before the experiment the solution contained : — 
Grains. 
Potash and sulphuric acid j^.lj?^ 
120-800 
After filtration through the soil, the whole solution con- 
tained potash, 56'936 grains ; consequently, 8*324 grains of 
potash were absorbed by 7000 grains of soil, or 1000 grains of 
soil absorbed in this experiment only 1"189 grains of potash. 
The sandy soil thus possessed the power of absorbing potash 
from a solution of sulphate of potash, in a very much more feeble 
