312 Absorption of Potash by Soils of known Composition. 
This amount of solid matter is nearly identical with that 
which the solution contained before the admixture, viz., 120 8 
grains ; but it is no longer exclusively sulphate of potash, but a 
combination of salts, in which sulphate of potash and sulphate 
of lime are most conspicuous. 
It will be remembered that this soil contained a good deal of 
carbonate of lime, and it will be seen at a glance that whilst a certain 
amount of potash became fixed, the sulphuric acid with which 
the potash was originally combined passed through the soil prin- 
cipally in union with lime. Before filtration the solution con- 
tained : — 
Grains. 
Sulphuric acid 55-540 
Potash .. .. 65-260 
120-800 
After filtration through the soil, the whole solution con- 
tained potash, 39*565 grains ; consequently, 25'695 grains of 
potash were absorbed by 1 lb. or 7000 grains of soil, and 1000 
grains of soil absorbed 3*671 grains of potash. 
The sulphuric acid in the liquid after filtration through the 
soil is distributed as follows : — 
23-141 grains are united with lime 1 
32'653 ,, potash and 
1-316 „ ,, magnesia. 
or 57-110 grains of sulphuric acid altogether. 
No absorption whatever of sulphuric acid thus took place. 
Indeed, the filtered liquid contained a little more sulphuric acid 
than originally existed in the 120 - 8 grains of sulphate of potash. 
This slight excess arises from a small quantity of sulphate of 
lime naturally existing in the soil, which augments the quantity 
produced by the sulphuric acid of the decomposed sulphate of 
potash. 
The preceding analytical results are interesting, as affording a 
positive proof of the fact that a solution of a single salt like 
sulphate of potash in percolating cultivated soils, gives rise to a 
great variety of new chemical soluble combinations, several of 
which exercise important functions in the nutrition of plants. 
Experiment No. 4. — With Sulphate of Potash on a Sterile Sandy 
Soil. 
For comparison with the preceding experiment, a solution of 
sulphate of potash was tried upon the sandy soil, of which the 
analysis will be found in the early part of this Paper (see p. 338, 
supra). 
