33S t Absorption of Potash by Soils of known Composition. 
Experiment No. 6. — On Sterile Sand. 
The soil selected for experiment was a very sterile, red, ferru- 
ginous .sand, containing scarcely any clay, mere traces of lime, 
and much oxide of iron, as will be seen by the following 
analysis : — 
Water ... .. 1-43 
*Or»;anic matter 3'39 
Oxides of iron and alumina 12-16 
Carbonate of lime -15 
Alkalies and magnesia "46 
Insoluble siliceous matter (sand) 82 - 41 
100-00 
♦Containing nitrogen *21 
Equal to ammonia *25 
3500 grains of this soil left in contact with the potash solution 
for lour days gave the following results : — 
Anhydrous Potash. 
Before tlie experiment the solution contained .. 33-96G 
After „ „ .. 12-413 
Totash absorbed by 3500 grains of soil . . 21*553 
1000 grains of this sterile sand consequently absorbed 16*16 
grains of caustic potash. In this series of experiments the 
following quantities of caustic potash were thus absorbed by 
1000 grains of 
| rotash (K 0). 
Grains. 
1. Calcareous soil 6 - 40 
2. Heavy clay 6'51 
3. Fertile sandy loam 5 - 69 
4. Pasture land G-57 
5. Marly soil 7 - 26 
(3. Sterile sand : 6 - 16 
These six soils differ greatly in their physical and chemical con- 
stitution, ranging from the heaviest clay land at the one extremity 
to the lightest of poor sands on the other. In every instance a 
considerable proportion of caustic potash was absorbed ; it may 
therefore be safely inferred that all soils, no matter what their 
composition, possess the power of separating caustic potash from 
its solution in water. This power, as has been already shown, 
differs in various kinds of soils, and is sometimes greater in 
poor or sterile soils than in good or rich arable or pasture land. 
However, with respect to the absolute quantity of potash which 
a soil is capable of absorbing, we must be careful to avoid 
a hasty judgment, for actual experiments show that the amount 
of potash which is fixed by a given quantity of soil depends 
