350 Absorption of Potash by Soils of known Composition. 
We might hence infer that chlorine had been absorbed by this 
soil ; but having previously ascertained the presence of ammonia 
in the soil, we may rather assume that this entered into com- 
bination with the chlorine, and so passed out ; while the 
potash, as evidently was the case, became fixed. Being- 
volatile, chloride of ammonium could not be present in the 
residue, hence the deficiency of chlorine in the analysis of the 
heated residue. That chlorine was not retained by the soil 
appears from a direct chlorine determination which I made in 
the filtered solution, instead of in the residue left on its evapora- 
tion. Calculated for the whole liquid (8 decigallons) I found 
49*392 of chlorine in the liquid after filtration through the soil, 
which agrees closely with the amount of chlorine in the chloride 
of potn^ium solution. 
It is remarkable that both the solutions of sulphate of potash 
and of chloride of potassium in passing through this soil lost 
but little potash, and caused the solution of a certain amount of 
ammonia contained in the soil. 
Experiment No. 8. — Absorption of Chloride of Potassium on a 
Marly Soil* 
Eight decigallons of the same solution as before were employed ; 
2 pints of the liquid filtered through the soil, on evaporation gave 
a residue weighing 32-781 grains, dried at 300° Fahr. 
The analysis of this residue yielded the following results : — 
Grains. 
Organic matter and water of comLi nation 1*230 
Soluble silica .. .. 1 -060 
Oxides of iron and alumina, with traces of phosphoric) .q^q 
acid / 
Sulphate of lime 1*558 
Chloride of calcium 7 - 890 
Chloride of magnesium "783 
Chloride of sodium '348 
Chloride of potassium 20976 
32-895 
In conformity with previous experience, a considerable quantity 
of chloride of potassium when in contact with this clay-marl was 
decomposed ; the potash of the decomposed salt alone became 
fixed in the soil, and the chlorine passed out principally in com- 
bination with calcium. • 
According to the preceding results, the whole solution (8 deci- 
gallons) after filtration through this soil, contained : — 
* The composition'of this soil 'will be found in p. 307. 
