50 Absorption of Phosphate of Lime ; and 
Tliis soil, it will be noticed, contains but little carbonate of lime, 
and much oxide of iron and of alumina in a hvdrated condition. 
In this state both these oxides unite readily with phosphoric acid 
to form combinations insoluble in water. When the acid biphos- 
phate of lime is brought into contact with alumina or oxide of iron, 
it loses part of its acid, which combines with these oxides, and 
becomes converted into basic or insoluble phosphate of lime. 
Clav soils invariably contain some, and in manv instances a 
good deal of these oxides. Theoreticallv thev mav therefore be 
regarded as good absorbers of soluble phosphate, even if they do 
not contain any carbonate of lime ; and the following experi- 
ments confirm this expectation. 
12 oz., or 5250 grains of this Subsoil, 109'33 grains of Superphosphate 
(containing 40*67 grains of Soluble Phosphate), and 1^ pint, or 13,125 
grains of Distilled Water, ucere mixed, as in Eaperiments A and B. 
After 24 hours, 3500 grains of the liquid being draura oft were found to con- 
tain o'70 grains of soluble phosphate, so that the whole 1^ pint 
of liquid held in solution 21'37 grains of bone-earth. Hence, 
since the whole amount of bone-earth in the mixture was 
40*67 grains, the 12 oz. of soil had absorbed 19'36 grains of 
bone-earth in 24 hours. 
Again, after 8 days (the bottle now containing 9625 grains of water), 2400 
grains of the liquid being filtered oflf j^erfectly clear, were 
found to contain 2"38 grains of bone-earth. Hence the 9625 
grains of water held in solution 9 o4 grains of bone-earth 
instead of 15'68, as after 24 hours' contact with the soil. 
Therefore, after 8 days, the soil had altogether absorbed 25*43 
grains of bone-earth. 
After 26 days (the bottle now containing 7225 grains of water), 2100 grains of 
clear liquid being drawn off, were found to contain l*'i4 grains 
of bone-earth. Hence the 7225 grains of water held in solu- 
tion 5*94 grains of bone-earth. Therefore, after 26 days, the 
soil had altogether absorbed 26*65 grains of bone-phosphate. 
It may be noticed that, after 24 hours, actually more soluble 
phosphate was contained in the liquid than passed into the soil. 
During the third stage of the experiment only 1*25 grains of 
bonc-earth were added to the soil. 
T he results are subjoined in a tabulated form. 
Supposing the whole solution to have been dravcn off in each stage of the 
Experiment, it would have coiitained — 
) Grains. 
After 24 hours 2137 of soluble phosphate. 
„ 8 days 13*01 
„ 26 days 10*87 
And in that case 1 2 oz. of this soil would have absorbed — 
After 24 hours 19*30 
„ 8 days 27-(J0 „ 
„ 26 days 29*80 
